ZeroTier and VPN configuration

Hello,

during my search how to share calendars in our intranet, I came across ZeroTier. At the moment a normal VPN is used for internet access. The challenge now is the configuration of mobile devices and laptops which use VPN for internet access.

Situation

  • ZT network has been created
  • caldav server has been setup with ZT

Configuration Debian

  • I would like to configure a debian laptop with VPN for internet access and with ZT only for caldav sync. How can I do it - maybe there is a link to a solution available?
    (After installing ZT I could ping the caldav server but could not establish a caldav connection - firewall on laptop issue? - VPN on router issue? - VPN on laptop was deactivated)

Configuration Android

  • I have read that only one VPN Client is allowed. And ZT has to be configured as VPN client as well. In this case I do not have my VPN for Internet access (surfing)? Correct? Any solution to that? Alternative to ensure normal internet access?
  • Does ZeroTier on Android requires Google Play Services?

And yes, I was looking for a solution in the internet but not successfully. If there is a solution out there, please send me the link.

BR Martin