I have noticed that every time I run rpm-ostree, for example to install a new rpm, it rebuilds the kernel modules for nvidia and v4l2loopback, which takes a few minutes.
On a normal Fedora install, I understand the build kmod rpm packages would be cached in /var/cache/akmods as long as the kernel and package version stay the same, so it’s not such a big deal. But in Silverblue, that doesn’t seem to happen.
Would the Fedora Silverblue devs consider supporting a persistent akmod cache?
Each update/installation/etc. using rpm-ostree is design to happen as if it was done “from scratch”, without previous state, thus why the module is rebuilt each time, in this case in a post script.
As workarounds, I would recommend either limiting the number of layered packages or using images from the Universal Blue project which bundle the NVIDIA drivers directly, thus avoiding the rebuild.
I’d recommend that you file a feature request upstream in GitHub - coreos/rpm-ostree: ⚛📦 Hybrid image/package system with atomic upgrades and package layering.