There's no algorithm here*, so use the different sorting options (for both posts and comments), as well as setting your favourite as default once you see what works for you.
* the different sort options are of course algorithms, but I mean there's no automatic, manipulative system like YouTube's "The Algorithm", Facebook, TikTok, etc.
Voting doesn't tune your algorithm, so I'd say only use downvoting for things that are low quality, trolling, in the wrong sub, duplicate posts, etc. Your votes aren't private, by the way - although Lemmy itself doesn't display voters' names, that info is in every server's database, and some other software in the Fediverse does show them.
There are quite a few apps available, I like Voyager on Android and I stick to the default website on my computer.
Are you saying you think it's ridiculous to end support "already"?
I think it's likely that anyone still using 486s isn't updating software anyway, so it's unlikely to matter aside from niches like retro devices. Luckily, open source means that if there's a genuine desire there'll probably be a fork to provide it.