!Friendica Support Finally I somehow(?) managed to make this settings appear in my Friendica account:

Wondering, now: Why do just a few channels appear in "Timeline Channels" and many more in "Filter Channels"? I don't really see a difference between the two of them.

What I actually want to achieve is having my /network timeline populated with posts of people I'm following (that's the "Everyone" channel which is essentially the "Following" circle without any other configuration) minus the stuff defined in the "Filter" channel (which is mostly keyword/tag based filtering). Right now, I'm either using the default network timeline (everything from following/followers plus tags and connector posts which is a lot) or the "Everyone" channel (which is just followed accounts but includes, in example, all the pastpuzzle/heardle/wordle/... stuff that I don't need to have around).