I have found the problem.
For some reason, part of the firmware with Debian 5.17 is not loaded
during boot. Manually loading the firmware fixes the problem and
everything works again. I have absolutely no idea why.
[...]
[ 27.227512] si2168 12-0064: firmware: direct-loading firmware
dvb-demod-si2168-b40-01.fw
[ 27.227515] si2168 12-0064: downloading firmware from file
'dvb-demod-si2168-b40-01.fw'
[ 27.876124] si2168 12-0064: firmware version: B 4.0.11
[ 27.887847] si2157 14-0060: found a 'Silicon Labs Si2157-A30 ROM 0x50'
[ 27.887929] si2157 14-0060: firmware: failed to load
dvb-tuner-si2157-a30-01.fw (-2)
[ 27.887931] si2157 14-0060: Can't continue without a firmware.
[ 27.906139] si2157 14-0060: found a 'Silicon Labs Si2157-A30 ROM 0x50'
[ 27.906145] si2157 14-0060: firmware: failed to load
dvb-tuner-si2157-a30-01.fw (-2)
[ 27.906147] si2157 14-0060: Can't continue without a firmware.
[...]
...
