RESOLVED
I was dumb. I was looking at the wrong line. There was a setting that says “Attempt Secure Boot” or something like that under the line “Secure Boot state” (or something like that).
I followed this official guide and I got the link for the IVSHMEM driver from here.
I got a Code 52 error, and I tried to turn off secure boot, but the option is disabled on Virt Manager’s UEFI settings.
Any idea how I can get around that?
Edit:
In this section:
<loader readonly="yes" type="pflash">/usr/share/OVMF/OVMF_CODE_4M.ms.fd</loader>
I changed it to OVMF_CODE_4M.fd, and it still left Secure Boot on.
Using OVMF_CODE.fd won’t let it boot.