So, some good news, and some bad news.
Good news: It seem the setting persists after rule-updates. So far APT is working fine on all my machines so far.
Bad News: Same problem now appeared for background updates of the Arduino IDE. Any download of board-JSON files for example from arcuino.cc throws an error.
So, I’ll search now for the interfering rule… Hint’s are appreciated. If I find something I’ll share it here.
EDIT: also reported here - it seems to be DNS related.
Which I can confirm already: ping arduino.cc fails with a “name resolution failed”. IDS disabled, it immediately works.
Though, I am not really sure why the other thread is considered as “solved”.