The staffers setup the new servers and did all the heavy-lifting.
As a user, I only had to point my client from Freenode to Libera (exactly one line change in my client config), run /msg nickserv register to register myself, run /msg chanserv register to register the channels I op-ed, and it was all done.
Total time spent was less than 30 minutes. The next few days, others did the same and the community started trickling in to the channels in the new servers. Seems seamless enough to me. I doubt such an easy migration is possible if Twitter disappears suddenly.
And yet userbase got decimated for most channels when moving from Freenode to Libera. Just because it was only 30 minutes (for you or for anyone) doesn't mean people will go through the effort.
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.
As a user, I only had to point my client from Freenode to Libera (exactly one line change in my client config), run /msg nickserv register to register myself, run /msg chanserv register to register the channels I op-ed, and it was all done.
Total time spent was less than 30 minutes. The next few days, others did the same and the community started trickling in to the channels in the new servers. Seems seamless enough to me. I doubt such an easy migration is possible if Twitter disappears suddenly.