The active userbase was not affected very much. (Note that some channels moved to OFTC, not Libera.) The lurker userbase was more than decimated – I think it about halved – but they were barely part of the communities, and there might not even have been anyone sitting behind the IRC clients.

anecodote only, but #ardour lost precisely zero users when moving from freenode to libera. just because people on channels you joined weren't willing to go through "the effort" doesn't mean that other people feel that way.

We switched to a bridged Libera IRC, FreeGameDev IRC, and a Discord channel, when the freenode drama happened, and our total lurker count went 10x.