Can you check you logfiles? There should be some information why you are only seeing a white page (Nextcloud-log in the data folder, but also your webserver logfile).
You need to have NC 9 running before upgrading further to NC 10 and then to NC 11.
Removing the owncloud packages also removes the webserver config files, I guess you have to set those settings again in your standard ssl config/vhost.