Hi @duplicati_fan, welcome to the forum!
Thanks for reporting what happened on your Debian system (and thanks @Folgore101 for continuing in Windows 10).
This is a known issue (Daylight Saving "changes" backup time) related to Duplicati storing time in UTC.
It’s mostly just an annoyance unless your backups are scheduled for specific days near midnight. For example, if you have a backup scheduled for 11:45PM on Sundays then this bug could cause the backup to be skipped because a DST change could cause the trigger time to happen on Monday morning.
I thought a fix was being looked at, but apparently it hasn’t progressed to completion. 