Preview generation

Is there a way to limit this to 1-2 cores so nextcloud is still accessible during preview generation?

cpulimit is quite handy with this. http://manpages.ubuntu.com/manpages/xenial/man1/cpulimit.1.html
And limit the sizes of the previews if you don’t need the biggest ones.

From my experimentation the preview limits no longer apply to the photos app - just the file manager. So this isn’t really an option either.