How to update docker-compose.yml with container images from private registry through TorizonOTA WebUI?

I have reproduced it with 2 different Apalis IMX8QM boards.
These are the steps I executed:

  1. Install VERSION=“5.1.0-devel-20210110+build.173 (dunfell)” on each edge device
  2. Provision edge device according to the TorizonOTA WebUI (works)
  3. Set up systemd service to login to private docker registry (works → can pull images manually when on device, for every logged in user; e.g. root/torizon)
  4. Upload custom package to TorizonOTA WebUI
  5. Initiate update of custom package via TorizonOTA WebUI

That’s it.
I guess prerequisites are to have a lot of random custom packages uploaded to the OTA server. I uploaded a lot and experimented with different naming schemes, docker compose versions, version numbers for the custom packages etc. so it’s very possible something got somehow twisted that way.