Realistically, a lot of projects simply have a Discord now. If you want to contribute, you have to go participate in that first.
As compared to the friction of another app even though they might be really great, I highly recommend trying out fluxer)
Then also if the developer has already created a discord server, then its hard to slightly migrate the existing users on their discord.
But I am sad about this development though, the community of open source or communities in general moving to discord does feel like moving to a walled garden (one which has increasingly more issues like trying to auto-detect your age and then asking for age-verification and plethora of other issues that a user is exposed to just by using the app which they might be using for the community itself, I really dislike it and I do wish if forums or something better could be used more as compared to discord.)
[Side-note: I built https://mirror.forum which is intended for communities to have both discord/fluxer & also other discord alternatives like stoat/matrix links to eventually help migrate users to these platforms and to help in finding the communities present in these spaces in the first place, I would love some feedback as the website is mostly crickets to be honest]
I highly highly recommend you checking it out, I must say that the first time I used it, I was mind blown that this open source discord alternative actually feels so usable in day-to-day lives.
There are many alternatives to be honest, stoat, matrix,fluxer but fluxer is the alternative I would recommend for public spaces.
The issue now is I think mostly just moving the userbase over to there.
[I have talked to the dev and tried to share it a few times on hackernews as a submission to help get more userbase as I think that HN would definitely love fluxer if it came to know more about it]
(Very slight advertisement but I have tried to build something in this space at https://mirror.forum which can allow a community to have discord,fluxer,matrix,stoat links in the same place for the purposes of discovery of servers in other places than discord and also for the migration of the userbase itself as i think that the problem of an open source solution is mostly solved and this was my attempt at trying to partially help in fixing the moving the userbase issue and making people more familiar with alternatives, though the website mostly has no activity nowadays and I would love activity to happen but I am unsure how to realistically approach so... that's why I am advertising perhaps, I would love to get feedback as well :-D)