I’ve been trying the COSMIC store and it looks like it killed my apt somehow. Apt says that there is a version mismatch between some libc6 packages, but I checked with dpkg and it all looks correct.

Apt says that I’ve a newer version of some packages but that is not true. Is there any way to fix this?
EDIT: Fixed formatting


Okay, I’ve read into your post a bit more and something is fishy. You have libc6 for different CPU-architectures installed.
Programs for i368 and amd64 should not be installed on the same machine. The error probably stems from that.
Run the following to find out the architecture:
uname -pIf it says ‘x86_64’ then it’s amd64 and if it’s something like 'i368’ then it’s that. Otherwise, your system might be really borked…
And then remove the wrong one.
FWIW, installing steam used to also install both architectures on my Fedora machine. I use the flatpak version now because it kept causing conflicts years ago.