TrialnError [1] filed a deletion request for nextcloud-app- mozilla_sync [2]: Unmaintained, Link to the add-on doesn't work anymore. If it was existing it would probably won't work anyway, because Nextcloud and Owncloud diverged quite significantly and Mozilla itself changed their Sync Service over the time in an incompatible way. Latest comment claims, that this add-on didn't work with Nextcloud 14+ So let this be gone? Somewhat informative: https://central.owncloud.org/t/what-happened-to-firefox-sync/10045 [1] https://aur.archlinux.org/account/TrialnError/ [2] https://aur.archlinux.org/pkgbase/nextcloud-app-mozilla_sync/