I spent about 30 seconds looking into how this is currently packaged in pmaports, here are some notes about what I think will need to happen to enable systemd support:
there's config in /etc/conf.d that will need to be available for the system service too (currently it's installed by openrc)
this config overwrites config from rmtfs-openrc
it seems like the rmtfs.service (in pmaports/systemd/systemd-services) isn't using anything from this config.. maybe that's a bug?
need to create a unit file to run this script, probably as Type=oneshot. This unit file should live in this repo, and not in pmaports/systemd-service
pmaports patch for msm-cros-efs-loader should 1) add a $pkgname-systemd subpkg, 2) add a like to system.preset in the postmarketos-base-systemd pkg to enable this unit, 3) move the conf.d into the main msm-cros-efs-loader pkg so it's installed for both openrc and systemd
@WeirdTreeThing pointed out in chat that we should use a unit drop-in to update any config for rmtfs, and not overwrite/replace the config in /etc/conf.d (but first maybe the rmtfs.service currently pkged in pmaports should be updated to use some path set in the config in /etc/conf.d ?)