I just installed Nextcloud on Arch and the official packages caused the most headaches I ever had within my 3 years of arch. In contrast I installed the official Jellyfin and Prometheus Server packages and they ran OOTB.
I ended up with not using the official packages but extracting the tar.bz2 into /var/www/nextcloud and slightly modifying the nginx config from their site. I had to move the inclusion of the MIME-Types file to a different block for nextcloud to deliver its CSS, SVGs and images. It wasn’t exactly straight-forward too considering permissions. I found it a beast compared to many other server software.