Desktop sync client is now (also) available in the Xtradeb PPA.
To install:
# add-apt-repository ppa:xtradeb/apps
# apt update
# apt install nextcloud-desktop
File manager integrations can be installed with:
- Stock Ubuntu with Nautilus:
$ sudo apt install nautilus-nextcloud - KDE Ubuntu with Dolphin:
$ sudo apt install dolphin-nextcloud - Ubuntu MATE with Caja:
$ sudo apt install caja-nextcloud - Ubuntu Mint with Nemo:
$ sudo apt install nemo-nextcloud