When I switch from the OSMC skin to Estuary, and I don’t change any other skin setting in Estuary afterwards, then the skin will be changed back to the OSMC skin after a reboot. However if I change any skin-related setting (e.g. the view level to Expert) after switching to Estuary and then do the reboot, the change persists. I got 2 log files: The first log was uploaded after the reboot that reset the skin to the OSMC skin. Then I switched to Estuary again and adjusted the view level and rebooted again and the skin change persisted. Then I uploaded the second log.
Btw it does not matter what I configured in Estuary before switching to the OSMC skin and back to Estuary. Any switch to the OSMC skin and back to Estuary without changing any skin-related setting afterwards will trigger this “bug”. So to reproduce this, I just have to change to the OSMC skin, then switch to Estuary and reboot the device. After the reboot, the skin is reset to the OSMC skin.
FYI this problem was not introduced with the Nexus update because I did experience it ca. 2 months ago when I was still on 19.4.