I see that there is a new channels feature here (or at least, new to me). Maybe a compromise would be to have offtopic be pretty broad in scope, but have it be a channel instead of a category for indexed and searchable threads? That seems easier to effectively opt out of.
I guess another question that this raises to me is whether this forum serves a different purpose than the slack/zulip/etc. I think that posting neat links and chatting about them with whoever happens to be on the forum and interested to engage at that time is cool, but if the ambition for discourse posts is that they are (i) worth indexing for search in the future and (ii) potentially long-running and references for future users, then maybe most off-topic discussions belong on the platforms that are a bit more ephemeral by design.
To be clear though, I also say this meaning no disrespect at all to @PetrKryslUCSD.