"Maybe some issues will be resolved by upgrading...."
They did :) I made a full backup with Plesk Onyx, deleted the whole server instance and set up a fresh Ubuntu 20.04 with Plesk Obsidian. Then recovered the backup with all files, databases, users, settings etc. It was suprisingly painless... Now everything seems to work fine and lessc I even installed just with apt install node-less
Though there may be some roadblocks, e.g. I was happy to have the backup in a remote location, because the backup was to big to upload. But simply setting the remote ftps made Plesk find the backup...
They did :) I made a full backup with Plesk Onyx, deleted the whole server instance and set up a fresh Ubuntu 20.04 with Plesk Obsidian. Then recovered the backup with all files, databases, users, settings etc. It was suprisingly painless... Now everything seems to work fine and lessc I even installed just with apt install node-less
Though there may be some roadblocks, e.g. I was happy to have the backup in a remote location, because the backup was to big to upload. But simply setting the remote ftps made Plesk find the backup...