https://www.linuxmintusers.de/index.php?topic=88747.0
My system: Mageia 9, x86_64, Plasma.
I have earlier updated to nextcloud-client 4.0.6 Appimage and it worked directly after update.
For some reason *), it no more shows its icon in systray (but it runs).
*) reboot, updates, hardware change (I moved disks to a less old computer, amdgpu -> nvidia470)
Workaround: use 4.0.4 until fixed. Get it from
https://download.nextcloud.com/desktop/releases/Linux/
Yes we should optimally search/open a bug @ Nextcloud, I am just too busy...
In Mageia 9 our packaged nextcloud-client is too old, due to compiling incompatibilities.
Fortunately it is back in Mageia 10, i have tried it, runs OK
BTW Nextcloud server too is back in Mageia 10.
