Hello,
I am not a heavy IRC user, but I'd say it makes most sense to just use Libera. It is essentially the same people that were running free-node running pretty much the exact same service, and I believe they are trying to make it extra easy to just switch, so this should be the least effort transition.
I believe IRC has served the GHC community quite well so far, and there is a reddit post by Ed Kmett that the normal Haskell channels have already been transitioned over, so I think it makes sense for GHC to stick with the rest of the Haskell community.
-Iavor