If you have something that needs the kernel headers that can be done by
installing the appropriate -headers package.
I think earlier you installed linux-libre-5.4, so that it would be
linux-libre-5.4-headers. Maybe I should mention this on the website just in
case.
The kernel headers are (currently) not installed by default. It's not clear
to me if they should be or not. I've done it both ways over the years where
they are and aren't. I usually get feedback from people both ways saying both
yes and no.
