Thank you so much for the replies, Igor and Ning, I appreciate it.
I tried installing linux-image-arm64 from the debian repo. but it didn't manage to boot, or even output anything on screen.
It seems the most recent version of linux-image-current-meson64 (22.08.7 / linux-5.19.17-meson64) does support loadable modules, but now a tangential problem has come to me:
wireguard-dkms won't build. ( It says "Error! The /var/lib/dkms/wireguard/1.0.20210606/5.19.17-meson64/aarch64/dkms.conf for module wireguard includes a BUILD_EXCLUSIVE directive which does not match this kernel/arch." )
How can I manage to have not just loadable kernel modules but also ZFS in kernel instead of user-space?
err, I'm sorry I wrote this question wrong, How can I have both ZFS in kernel space like I did by installing version 22.08.7 of linux-image-current-meson64, and also wireguard-dkms?