congratulations @fepitre on the qubes-contrib repo! very exciting.
Following the guide for qubes-tunnel:
instead of LINK IS UP I get Ready to start link notifications. it’s not clear to me what I need to do to “start the link”.
it would be great to include this in the set-up documentation (I can do so once you let me know the missing steps).
The link starts automatically after it says ‘Ready’.
To troubleshoot the connection you can monitor the systemd service that
controls the vpn client with ‘journalctl -u qubes-tunnel’.
perfect, thanks @tasket - and more importantly for qubes-tunnel and qubes-vpn-support 
got the errors I needed to successfully troubleshoot (needed to provide absolute links in the config file). I’ll add a line to the setup in case folks needs to troubleshoot.