Hi Boris,
the last time I installed a fresh new image, external disks (storage) configuration through GUI was a piece of cake.
The system recognized that there was an existing RAID1 and offered 2 options: disks and partitions. It was sufficient choosing “partitions” and /data was mounted perfectly.
Now (System:2261; Installer:639) , in place of that, the page settings –> storage shows a blank page but, for a tenth of a second, it is possible to read “no external disks found” below the switch partitions/disks.
My RAID1 was built with mdadm and, as far as I remember, I have never converted it to BTRFS (assuming that is possible) nor rebuilt it because I don’t have enough room anywhere to backup it 
I’m sendng you a clean LOG file where, immediately after reboot, I access the page “storage” in the GUI.
p.s. this the page storage as I could see it in december 2022, I have found an old posts of mine.
p.p.s. it seems like I have to reassemble the RAID before going ahead:
root@syncloud:~# lsblk
NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT
loop0 7:0 0 164M 1 loop /snap/platform/2261
loop1 7:1 0 129M 1 loop /snap/platform/2161
sda 8:0 0 3.7T 0 disk
sdb 8:16 0 3.7T 0 disk
mmcblk0 179:0 0 59.5G 0 disk
├─mmcblk0p1 179:1 0 256M 0 part
└─mmcblk0p2 179:2 0 59.2G 0 part /
root@syncloud:~#
but I have a problem: the package mdadm cannot be installed anymore.
Look here:
root@syncloud:~# apt-get install mdadm
Reading package lists... Done
Building dependency tree... Done
The following additional packages will be installed:
exim4-base exim4-config exim4-daemon-light file guile-2.2-libs libevent-2.1-6 libfribidi0 libgc1c2
libgnutls-dane0 libgsasl7 libkyotocabinet16v5 libltdl7 liblzo2-2 libmagic-mgc libmagic1 libmailutils5
libmariadb3 libntlm0 libpython2.7 libpython2.7-minimal libpython2.7-stdlib libunbound8 mailutils
mailutils-common mariadb-common mime-support mysql-common psmisc xz-utils
Suggested packages:
exim4-doc-html | exim4-doc-info eximon4 spf-tools-perl swaks dns-root-data mailutils-mh mailutils-doc
dracut-core
The following NEW packages will be installed:
exim4-base exim4-config exim4-daemon-light file guile-2.2-libs libevent-2.1-6 libfribidi0 libgc1c2
libgnutls-dane0 libgsasl7 libkyotocabinet16v5 libltdl7 liblzo2-2 libmagic-mgc libmagic1 libmailutils5
libmariadb3 libntlm0 libpython2.7 libpython2.7-minimal libpython2.7-stdlib libunbound8 mailutils
mailutils-common mariadb-common mdadm mime-support mysql-common psmisc xz-utils
0 upgraded, 30 newly installed, 0 to remove and 0 not upgraded.
Need to get 15.8 MB of archives.
After this operation, 83.2 MB of additional disk space will be used.
Do you want to continue? [Y/n] y
Err:1 http://deb.debian.org/debian buster/main arm64 libmagic-mgc arm64 1:5.35-4+deb10u2
404 Not Found [IP: 146.75.62.132 80]
Err:2 http://deb.debian.org/debian buster/main arm64 libmagic1 arm64 1:5.35-4+deb10u2
404 Not Found [IP: 146.75.62.132 80]
Err:3 http://deb.debian.org/debian buster/main arm64 file arm64 1:5.35-4+deb10u2
404 Not Found [IP: 146.75.62.132 80]
Err:4 http://deb.debian.org/debian buster/main arm64 mime-support all 3.62
404 Not Found [IP: 146.75.62.132 80]
Err:5 http://deb.debian.org/debian buster/main arm64 xz-utils arm64 5.2.4-1+deb10u1
404 Not Found [IP: 146.75.62.132 80]
Err:6 http://deb.debian.org/debian buster/main arm64 exim4-config all 4.92-8+deb10u6
404 Not Found [IP: 146.75.62.132 80]
Err:7 http://deb.debian.org/debian buster/main arm64 exim4-base arm64 4.92-8+deb10u6
404 Not Found [IP: 146.75.62.132 80]
Err:8 http://deb.debian.org/debian buster/main arm64 libevent-2.1-6 arm64 2.1.8-stable-4
404 Not Found [IP: 146.75.62.132 80]
Err:9 http://deb.debian.org/debian buster/main arm64 libunbound8 arm64 1.9.0-2+deb10u2
404 Not Found [IP: 146.75.62.132 80]
Err:10 http://deb.debian.org/debian buster/main arm64 libgnutls-dane0 arm64 3.6.7-4+deb10u8
404 Not Found [IP: 146.75.62.132 80]
Err:11 http://deb.debian.org/debian buster/main arm64 exim4-daemon-light arm64 4.92-8+deb10u6
404 Not Found [IP: 146.75.62.132 80]
Err:12 http://deb.debian.org/debian buster/main arm64 libgc1c2 arm64 1:7.6.4-0.4
404 Not Found [IP: 146.75.62.132 80]
Err:13 http://deb.debian.org/debian buster/main arm64 libltdl7 arm64 2.4.6-9
404 Not Found [IP: 146.75.62.132 80]
Err:14 http://deb.debian.org/debian buster/main arm64 guile-2.2-libs arm64 2.2.4+1-2+deb10u1
404 Not Found [IP: 146.75.62.132 80]
Err:15 http://deb.debian.org/debian buster/main arm64 libfribidi0 arm64 1.0.5-3.1+deb10u2
404 Not Found [IP: 146.75.62.132 80]
Err:16 http://deb.debian.org/debian buster/main arm64 libntlm0 arm64 1.5-1+deb10u1
404 Not Found [IP: 146.75.62.132 80]
Err:17 http://deb.debian.org/debian buster/main arm64 libgsasl7 arm64 1.8.0-8+deb10u1
404 Not Found [IP: 146.75.62.132 80]
Err:18 http://deb.debian.org/debian buster/main arm64 liblzo2-2 arm64 2.10-0.1
404 Not Found [IP: 146.75.62.132 80]
Get:19 http://deb.debian.org/debian buster/main arm64 libkyotocabinet16v5 arm64 1.2.76-4.2+b1 [267 kB]
Err:20 http://deb.debian.org/debian buster/main arm64 mailutils-common all 1:3.5-4
404 Not Found [IP: 146.75.62.132 80]
Err:21 http://deb.debian.org/debian buster/main arm64 mysql-common all 5.8+1.0.5
404 Not Found [IP: 146.75.62.132 80]
Err:22 http://deb.debian.org/debian buster/main arm64 mariadb-common all 1:10.3.34-0+deb10u1
404 Not Found [IP: 146.75.62.132 80]
Err:23 http://deb.debian.org/debian buster/main arm64 libmariadb3 arm64 1:10.3.34-0+deb10u1
404 Not Found [IP: 146.75.62.132 80]
Err:24 http://deb.debian.org/debian buster/main arm64 libpython2.7-minimal arm64 2.7.16-2+deb10u1
404 Not Found [IP: 146.75.62.132 80]
Err:25 http://deb.debian.org/debian buster/main arm64 libpython2.7-stdlib arm64 2.7.16-2+deb10u1
404 Not Found [IP: 146.75.62.132 80]
Err:26 http://deb.debian.org/debian buster/main arm64 libpython2.7 arm64 2.7.16-2+deb10u1
404 Not Found [IP: 146.75.62.132 80]
Err:27 http://deb.debian.org/debian buster/main arm64 libmailutils5 arm64 1:3.5-4
404 Not Found [IP: 146.75.62.132 80]
Err:28 http://deb.debian.org/debian buster/main arm64 mailutils arm64 1:3.5-4
404 Not Found [IP: 146.75.62.132 80]
Err:29 http://deb.debian.org/debian buster/main arm64 mdadm arm64 4.1-1
404 Not Found [IP: 146.75.62.132 80]
Err:30 http://deb.debian.org/debian buster/main arm64 psmisc arm64 23.2-1+deb10u1
404 Not Found [IP: 146.75.62.132 80]
Fetched 267 kB in 4s (62.7 kB/s)
E: Failed to fetch http://deb.debian.org/debian/pool/main/f/file/libmagic-mgc_5.35-4+deb10u2_arm64.deb 404 Not Found [IP: 146.75.62.132 80]
E: Failed to fetch http://deb.debian.org/debian/pool/main/f/file/libmagic1_5.35-4+deb10u2_arm64.deb 404 Not Found [IP: 146.75.62.132 80]
E: Failed to fetch http://deb.debian.org/debian/pool/main/f/file/file_5.35-4+deb10u2_arm64.deb 404 Not Found [IP: 146.75.62.132 80]
E: Failed to fetch http://deb.debian.org/debian/pool/main/m/mime-support/mime-support_3.62_all.deb 404 Not Found [IP: 146.75.62.132 80]
E: Failed to fetch http://deb.debian.org/debian/pool/main/x/xz-utils/xz-utils_5.2.4-1+deb10u1_arm64.deb 404 Not Found [IP: 146.75.62.132 80]
E: Failed to fetch http://deb.debian.org/debian/pool/main/e/exim4/exim4-config_4.92-8+deb10u6_all.deb 404 Not Found [IP: 146.75.62.132 80]
E: Failed to fetch http://deb.debian.org/debian/pool/main/e/exim4/exim4-base_4.92-8+deb10u6_arm64.deb 404 Not Found [IP: 146.75.62.132 80]
E: Failed to fetch http://deb.debian.org/debian/pool/main/libe/libevent/libevent-2.1-6_2.1.8-stable-4_arm64.deb 404 Not Found [IP: 146.75.62.132 80]
E: Failed to fetch http://deb.debian.org/debian/pool/main/u/unbound/libunbound8_1.9.0-2+deb10u2_arm64.deb 404 Not Found [IP: 146.75.62.132 80]
E: Failed to fetch http://deb.debian.org/debian/pool/main/g/gnutls28/libgnutls-dane0_3.6.7-4+deb10u8_arm64.deb 404 Not Found [IP: 146.75.62.132 80]
E: Failed to fetch http://deb.debian.org/debian/pool/main/e/exim4/exim4-daemon-light_4.92-8+deb10u6_arm64.deb 404 Not Found [IP: 146.75.62.132 80]
E: Failed to fetch http://deb.debian.org/debian/pool/main/libg/libgc/libgc1c2_7.6.4-0.4_arm64.deb 404 Not Found [IP: 146.75.62.132 80]
E: Failed to fetch http://deb.debian.org/debian/pool/main/libt/libtool/libltdl7_2.4.6-9_arm64.deb 404 Not Found [IP: 146.75.62.132 80]
E: Failed to fetch http://deb.debian.org/debian/pool/main/g/guile-2.2/guile-2.2-libs_2.2.4+1-2+deb10u1_arm64.deb 404 Not Found [IP: 146.75.62.132 80]
E: Failed to fetch http://deb.debian.org/debian/pool/main/f/fribidi/libfribidi0_1.0.5-3.1+deb10u2_arm64.deb 404 Not Found [IP: 146.75.62.132 80]
E: Failed to fetch http://deb.debian.org/debian/pool/main/libn/libntlm/libntlm0_1.5-1+deb10u1_arm64.deb 404 Not Found [IP: 146.75.62.132 80]
E: Failed to fetch http://deb.debian.org/debian/pool/main/g/gsasl/libgsasl7_1.8.0-8+deb10u1_arm64.deb 404 Not Found [IP: 146.75.62.132 80]
E: Failed to fetch http://deb.debian.org/debian/pool/main/l/lzo2/liblzo2-2_2.10-0.1_arm64.deb 404 Not Found [IP: 146.75.62.132 80]
E: Failed to fetch http://deb.debian.org/debian/pool/main/m/mailutils/mailutils-common_3.5-4_all.deb 404 Not Found [IP: 146.75.62.132 80]
E: Failed to fetch http://deb.debian.org/debian/pool/main/m/mysql-defaults/mysql-common_5.8+1.0.5_all.deb 404 Not Found [IP: 146.75.62.132 80]
E: Failed to fetch http://deb.debian.org/debian/pool/main/m/mariadb-10.3/mariadb-common_10.3.34-0+deb10u1_all.deb 404 Not Found [IP: 146.75.62.132 80]
E: Failed to fetch http://deb.debian.org/debian/pool/main/m/mariadb-10.3/libmariadb3_10.3.34-0+deb10u1_arm64.deb 404 Not Found [IP: 146.75.62.132 80]
E: Failed to fetch http://deb.debian.org/debian/pool/main/p/python2.7/libpython2.7-minimal_2.7.16-2+deb10u1_arm64.deb 404 Not Found [IP: 146.75.62.132 80]
E: Failed to fetch http://deb.debian.org/debian/pool/main/p/python2.7/libpython2.7-stdlib_2.7.16-2+deb10u1_arm64.deb 404 Not Found [IP: 146.75.62.132 80]
E: Failed to fetch http://deb.debian.org/debian/pool/main/p/python2.7/libpython2.7_2.7.16-2+deb10u1_arm64.deb 404 Not Found [IP: 146.75.62.132 80]
E: Failed to fetch http://deb.debian.org/debian/pool/main/m/mailutils/libmailutils5_3.5-4_arm64.deb 404 Not Found [IP: 146.75.62.132 80]
E: Failed to fetch http://deb.debian.org/debian/pool/main/m/mailutils/mailutils_3.5-4_arm64.deb 404 Not Found [IP: 146.75.62.132 80]
E: Failed to fetch http://deb.debian.org/debian/pool/main/m/mdadm/mdadm_4.1-1_arm64.deb 404 Not Found [IP: 146.75.62.132 80]
E: Failed to fetch http://deb.debian.org/debian/pool/main/p/psmisc/psmisc_23.2-1+deb10u1_arm64.deb 404 Not Found [IP: 146.75.62.132 80]
E: Unable to fetch some archives, maybe run apt-get update or try with --fix-missing?
root@syncloud:~#
Thanks for your help.
Simone