enable read-only sysroot

[boredsquirrel]

This is a feature implemented in F37 but its opt-in, which is imo pretty useless as probably everyone benefitting from it would not manually enable that.

sudo rpm-ostree kargs --append-if-missing=rw

sudo ostree config --repo=/sysroot/ostree/repo set "sysroot.readonly" "true"

sudo systemctl reboot

This may cause breakages, but probably not. If there are any kernel changes or layered packages this may cause troubles or has to be applied afterwards.