The Seagate Ironwolf Pro 22TB only shows 20 TB! By the way, I find it very cheeky of Synology to no longer test external drives.

Yes, there is also a simple solution for the warnings for non-syno disks: set "support_disk_compatibility" to "no".

You can find complete instructions on how to do this on the Swissmakers GmbH blog: https://swissmakers.io/synology-d...
I also bought my NAS via Digitec, run it with 4 WD red 18TB drives and am happy with it. :)

Probably yes! This means that it works, but the disks are displayed with drive status 'unverified'. Officially, only Syno disks are 100% supported for this model:
https://www.synology.com/en-eu...

I myself don't care.... it works with my 12TB WD Red Plus ;)

Yes