I'm getting many bots with IPs that aren't blacklisted from Eastern Europe countries so I rather just block the countries

You can do that with AuthMe, since this plugin is mainly for Offline Mode servers, this won't be max priority, but I'll see what I can do in 6.0.

Unfortunately i'm using another plugin for authentication other than authme

Eh, that's what I imagined. Will work on it, since AntiJoinBot 6 will be Modular, you can enable/disable what modules you want and they will not impact on performance.

This also makes it easier for me to add new protection modules in the future.

Is there an ETA for when to expect 6.0?

Unfortunately no.