yes i second matrix. it's different from discord in a lot of ways, but it's still a pretty seamless transition. for anyone who wants to host matrix, i recommend the continuwuity homeserver software. it's much easier to host than synapse and is significantly faster for 99% of use cases

if you're just trying use matrix, i prefer cinny over element for the client. cinny's ui is also very similar to discord's and it handles space/room grouping very intuitively. there's also fluffychat (less feature rich) and schildichat (element fork), among others. however, element is currently the only client which fully supports voice chat

for instances, i recommend choosing something other than matrix.org. right now, matrix is barely decentralized because the vast majority of users choose matrix.org, which isn't great. also matrix.org collects a lot of data and requires more information to register than most servers. some other good public instances are:

• tchncs.de
• unredacted.org
• catgirl.cloud
• calitabby.net

there are also many, many smaller public instances, but it's probably better to choose a relatively big one for moderation reasons. a lot of people think matrix is dead or no one uses it, but there are plenty of active communities if you know where to look

for your friends who refuse to quit discord for some reason, matrix's ecosystem also has lots of bridges. if you're willing to self host, i recommend out of your element. the only caveat is that it doesn't support e2ee rooms