There is already a nextcloud version of the (owncloud) client. Reproducible: Always
Indeed, I was tracking their progress since the comment in: https://nextcloud.com/blog/secure-monitor-and-control-your-data-with-nextcloud-10-get-it-now/ It looks like the 2.2.3 theming tarball is available in github, I will take a look
A few ebuild cleanups and adaptations on the owncloud-client ebuild later, there is now nextcloud-client-2.2.3 in tree
Thanks! :-)