You said it yourself — you're new to self hosting, and CasaOS fits what you want to host. As a starting point for getting rid of hosted services, go with that for a start.
Sure, you won't immediately be getting your hands dirty mucking about with dockers and stuff, but you will have your working home server. For learning and experimentation, I second @Scipitie@lemmy.dbzer0.com's plan B — use another machine to test building the same setup on a base Linux system.
If you're like me you probably have an old laptop lying around that wouldn't be great as an always up, day to day server, but as a testing environment to mess around with docker containers it should be fine?
I mean, yeah. Especially when the content of your flawlessly customised site is federated to thousands other activity pub enabled sites with different stylesheets and aesthetics. That isn't a problem with Mastodon per se, it's just the nature of federation.
I do agree with your broader point that Mastodon has become synonymous with fediverse microblogging, which again is what most people associate with the fediverse, period.
30% self-congratulatory talk about how popular bluesky is this week.
TBF, Mastodon was the same when I joined. I just muted all mention of "mastodon" + variations, Bob's your uncle. Navel gazing meta discourse is the least exciting updates on any platform.
It is still funny to visit random egg profiles on there and see they only tooted once, two years ago, saying "so this is mastodon, wonder how this works" and then never again.
I'm not criticising my right to put in extra work to make promising efforts available on platforms that do not track users; I criticise the fact that the developers didn't do this in the first place.
But good work putting the onus on me, you complete corporate rando.
There is also MicroBlogPub, although development has wound down in the past year. I spun up a test instance before that, though, and it does what it says on the tin.
Of late I've tried out the Translate You Android app. Not necessarily an endorsement of the app itself, but it offers a selection of 9 translator services, a few of which are libre.
Certainly LibreTranslate and Lingva [my bad, it's a GTranslate front-end] Apertium are open source, probably a few more on their list. Give them a try and see which works best for you!
Don't worry, most of us won't. It'll trickle down through abstraction layers from CLW level work to us end users eventually 🙂