pretty much every project out there could use some help.

to find ideas, start with the software you are using. is there any that you like using a lot where you feel that something could be improved? you can also look at websites that you are using, see if any of them are volunteer based.

if that doesn't lead to anything, look at your skills, or skills you'd like to learn. then look for projects based on that.

and finally just browse issues of various projects, search for "help wanted" or "good first issue" or similar and simply try out fixing one such issue, then see if you like working with that project.

there also was an hn thread similar to this one some time ago where people posted projects that they need help with: https://news.ycombinator.com/item?id=42157556

i also have a project that i could use some help with, but the learning curve is a bit high (or rather the setup work you need to do to before you can start coding): https://news.ycombinator.com/item?id=42159045