Its possible that using whatever the latest Allocs mod is with the current version of RAT3, things should work mostly as they do now. However, please note that there will be NO SUPPORT for RAT3 on A21, you're on your own. 
That being said, I'm currently working on RAT4, which will be A21 compatible and supported. Expect a beta to hit the Discord channel soon(ish) (week or so, depends on when I get things stable enough to test, etc).
Once I think RAT 4 is stable enough to release, I'll post it here on this website in the Resources section as usual.
As always, thanks for your support and keeping RAT alive! Your feature requests, bug reports and general activity in Discord and other places are what keeps me coding. =)

That being said, I'm currently working on RAT4, which will be A21 compatible and supported. Expect a beta to hit the Discord channel soon(ish) (week or so, depends on when I get things stable enough to test, etc).
Once I think RAT 4 is stable enough to release, I'll post it here on this website in the Resources section as usual.
As always, thanks for your support and keeping RAT alive! Your feature requests, bug reports and general activity in Discord and other places are what keeps me coding. =)