I released iTerm2 version 3.4.0 this morning with Big Sur support. Please update because 3.3 has various issues with it.
Wat?
"Oh, I think I see what happened. Here's what's going on:
* I'm currently only making 3.4.0 available through software update for Big Sur users to slow the rollout in case there is a critical bug.
* I should not have removed 3.3.12 from the appcast file. That's why you're being told that 3.1.7 is the newest version. I've put it back.
If you want to upgrade to 3.4.0, you can download it from https://iterm2.com/downloads or else wait a few days until I push it out for everyone."