Ok.. I used Sid repository, and upgraded to 2.1.2
No change with Deluge, checking more ideas, also the statistics screen is finally fixed now ))

Well the PPA for older ubuntu you linked not working - it gives an errors, saying 'can not connect to server', essentially, and I have tried it before, on my own, ofc, I tend to read first before I start to ask for help :) " The repository may no longer be available or could not be contacted be...

I've been using Deluge for years, starting with Debian 8. And never had any problems with it. About a month ago I have upgraded to Debian 12 (from 11) and installed the latest Deluge. The 'Disk Cache' not working, no matter what numbers I enter - nada. Thing is I'm seeding a lot of torrents, about 5...