Right, my mistake, I’m using systemd-boot, not grub. It’s been a long time since I’ve looked at this config. So, I changed /etc/kernel/cmdline to include the parameter lsm=landlock,lockdown,yama,integrity,apparmor,bpf (the trick to getting the kernel to update was to remove and reinstall the kernel with mhwd-kernel -r and mhwd-kernel -i, which could probably also be done from Manjaro Settings). Note that I have edits to /etc/kernel/cmdline for a needed LUKS parameter, among other things.
That fixes pacman, but does not fix the login issue with GDM. So, it’s useful, but unrelated…