the BTF issue was actually an upstream kernel change (it also hit Debian [0][1] a while later, and I assume other distros as well) - it broke the ABI compatibility, so even though the booted kernel and the modules on disk were in fact compatible, the kernel refused to load them if they came from a different build. the workaround on affected systems is to reboot, or if that is not an option, temporarily downgrade the installed kernel image + modules - both have the effect of forcing a match between the booted kernel and the modules loaded from disk. more recent kernel versions provided by Proxmox have the BTF-for-modules disabled, thus working around the issue.