Here's some documentation you might be unaware of as to how this plugin could potentially be fixed to allow for it to work after its depreciated. I'm unsure if that's possible though
https://discord.com/developers/docs/game-sdk/discord-voice
https://discord.com/developers/docs/game-sdk/lobbies#connectvoice
https://github.com/deathbeam/discord-game-sdk-java
I'll probably look into it some more myself once i have more time to do it. actually, i'm having trouble finding anything saying that the discord features themselves are being discontinued

I've already seen most of those projects, and yeah, the project could totally continue after the discontinuation date! I couldn't ever find anything on why those features would stop working besides the notice here. I'm probably going to stick with discord-game-sdk4j until the features stop working, and I'll work on switching to another library once some other problems are fixed.

Did you read big red notice on Discord website? (first link)

Voice will be removed from gamesdk features on Discord side so different library won't help