I’d try upgrading everything but the kernel for a test, even if it complains “partial upgrade” it should work fine. If the network still works then the problem is likely with the kernel version. As far as I can tell 6.7.6 did not touch the igb driver though.
Aside, I think the “unmount root” thing may well be unrelated.
edit: quite likely Networkmanager 1.46.0-1 Update Breaks internet connectivity