Comment 1 for bug 1999082

What happened here is that we dropped the 510 driver in lrm 5.4.0-135.152+1, transitioning it to the 515 driver. It therefore did not produce a 5.4.0-135.152+1 version of linux-modules-nvidia-510-server-5.4.0-135-generic. Ubuntu always keeps the latest version of a binary package in the archive, even if the source that produced it has been superseded. Because of that, the 5.4.0-135.152 version of linux-modules-nvidia-510-server-5.4.0-135-generic is sticking around. 5.4.0-135.152 correctly had a strict versioned dep on a matching linux-signatures package, and that linux-signatures package was superseded by a new one. Superseded packages *are* dropped from the archive, so that dependency can no longer be met.

TLDR; this is all normal (though not ideal) behavior, and this one is particularly confusing because we dropped (and transitioned) the 510 driver during a refresh of the drivers for a kernel that previously had a 510 driver.

Lesson: Installing modules for anything other than the latest kernel update is not supported, even if those modules appear to still be available in the archive.