The Nextcloud client does add itself to autostart on Linux, however I don’t see a tray icon by default. I’ll show you how to fix it.
After the installation, Nextcloud creates a bad entry to the “autostart”, which needs to be replaced with the correct entry as follows:
Go to your “start menu” and look for “startup” or “autostart” depending on your desktop environment. You should find an entry that opens the settings to add applications to the “autostart”.
Once in those settings, you will find an entry for “Nextcloud”.
Delete or disable it.
Now add a new application to the list, and choose “Nextcloud desktop sync client”.
Next time you sign in, you will see the correct Nextcloud client (desktop entry) has started, and the tray icon should be visible too.
That’s all there is to it!
[UPDATE] If it still does not work for you, try disabling the built-in Nextcloud autostart in the client settings (uncheck “Launch on System Startup”) and create a new autostart entry with the command “killall nextcloud” with a delay of 3 seconds, and set the previously added Nextcloud entry to a delay of 5 seconds. That way, any bad entry that started in the background will be killed and the real entry can be started with desktop integration and tray icon.
I can’t see the default Nextcloud entry
In some cases that entry will be visible the next time you sign in, then proceed as stated above. If it’s still not there, skip the part where you delete or disable the default entry, and instead just add a new entry as stated above.