Usually new devices are added in new major versions. So if a device is not included in 22.03.X but there is a snapshot, it may be included in 23.YY.X. You can sysupgrade to that version later from your snapshot.
How can I judge whether the EdgeRouter 4 is just lower on priority list because more expensive and less frequent in the field or considered older and a candidate for phased-out support?
IIRC, the device info pages require manual or semi-manual updates. Given the sheer number of devices supported by OpenWrt, it is not uncommon for some of the devices to be 'left behind' with respect to out of date info pages, even when they are indeed included in the latest OpenWrt builds.
right... and I think this is a somewhat manual process, although I could be wrong... I'm sure @tmomas will clarify. If it is manual or semi-manual, it wouldn't be surprising that some get left out of the info page update process for whatever reasons (likely by mistake/oversight).
Anyway, I am quite impressed. I already built a custom image using a linux x86 machine in Google Cloud (as I don't have one with this architecture at home).
But I didn't know that on this page I can also add packages to a release build and create a custom image. Chapeau!
Downgrading is usually pretty straight forward... use the standard sysupgrade process. Just make sure that youdo not keep settings. Reconfigure from scratch.
A backup of your current config can be useful as a human readable reference while you reconfigure... but do not restore a backup from a different version.