Just wondering, is it safe to use kernel 5.4 or 5.10 with Debian Buster
packages?
Kernel has stable userland ABI. Any user program (like bash or nginx) should be compatible with any future kernel release.
But kernel doesn't guarantee kernel modules ABI (even API is not stable).
So, regular apps should work. But packages that contain kernel modules or kernel-specific tools will probably fail.
You may also face problems with settings in "apt.conf.d" that depend on certain kernel.
Isn't it better to install debian bullseye?
It has 5.10 and will be released soon