I do hope that ppa’s that are clearly marked up as being the developers ppa are run by nextcloud…
… https://launchpad.net/~nextcloud-devs/+archive/ubuntu/client…
You can already find Nextcloud Desktop client packages included in openSUSE Tumbleweed, Arch Linux and Fedora. You can find Ubuntu/Debian packages in this PPA. Packages for Alpine Linux over here. See the latest state and more packages in this post on our forums. Can’t find packages? Ask your distribution or contribute to creating them!