I think all organizations end up protecting their branches at the CI level to completely shut down on rewriting past history. It just makes no sense in most cases.

On how individual devs deal with that, the alternative to the massive squashing is to me cherry-picking one’s changes against the upstream.

The bigger the branches diverge the more of a PITA it is to herry-pick, but it also means the feature being worked on is becoming too big/too much in conflict to be kept alive separate for long. My own target is 3 to 4 meaningful commits per-branch, excluding MR comments, and it works fine, mostly,