My hand joints are getting better finally and I wanna learn an instrument. The thing is, I'm dumb and have struggled really badly with reading music in the past.
The recorder. It's easy to get started, there is a lot of good information online (look up Sarah Jeffery), and professional plastic instruments are very cheap. It also requires no special care and doesn't need maintenance, since it has no moving parts.
The downside is that in order to play larger recorders your hands need to stretch a bit, so I'm no sure if that is a problem if you have joint issues.
The other option is a hand ocarina, but it is very hard to even make a sound, even harder to make it clear and consistent. Also you need to play entirety by ear. It's a fun challenge, though.