My two ideas that could come to mind is
1: Yes, try to build the release template on an older OS, right now the one I personally use for my game is Ubuntu 22.04 LTS
2: I’m sure you already made sure of this, but you need to use the same exact encryption key both during the compilation and inside the export window on Godot, and normally, you shouldn’t include the [ and ] symbols for it, as you showed here in your post. (Again, I’m sure it’s just for display purposes, just trying to rule everything out.
Edit: Also make sure you switched to the correct tag in git, you can list all the tags with
git tag -l and make sure you switch to the exact same version you’re currently using.