Okay, I'm a stubborn idiot and couldn't go to sleep. But I got my SGP621 updated to 3.2.1.19! Here's what I did (having fresh 2.2.1.18 that is):

• Disable adaptation repositories:
  ssu dr adaptation-community
  ssu dr adaptation-community-common
  pkcon refresh
• Update to 3.0.0.8 (stop release):
  ssu release 3.0.0.8
  zypper ref -f
  version --dup
  sync
  reboot
• Enable adaptation repositories:
  ssu er adaptation-community
  ssu er adaptation-community-common
  pkcon refresh
• Update to 3.2.1.19
  ssu release 3.2.1.19
  zypper ref -f
  version --dup
  sync
  reboot

And that's about it! What this tells me that there is some kind of incompatibility between the newest adaptation packages (the most current update has three days ago - which is great!) and Sailfish <= 3.0.0.8 at least, but using the dance choreography above, it all works out!

Some users commented that the device would not power down correctly, but my device does, at least now. To my great surprise, I can now watch YouTube videos using YTplayer (my openrepos version)! I do have Webcat installed, perhaps it pulled in some gstreamer packages or something..?

If that's not impressive enough, the built-in Browser gives me 1080p YouTube videos with no problems whatsoever! Even my XA2 Ultra can't do that!

The only hiccup is GPS, which for whatever reason stopped working when I was testing GPSinfo on 2.2.1.18. It worked for a while, but it just won't work again. There's no location blip next in top left (right) corner. The location icon in the top menu work as expected but it does nothing now.

Now that I'm up to date, is there anything to test or debug? I'm happy and impressed with the state of the port so far, but I would love to see an updated build, both because of Sailfish version, and polishing out hardware adaptation bugs. I still haven't tested mobile data, calls and texts, and I don't have a memory card inserted, but I think I'll get to that tomorrow. Maybe.

Thanks again for your hard work, everyone!

Edit: typo in "ssu er" commands