After adding IPv6 support here: https://github.com/vyos/vyos-1x/commit/bb9f99853c723c5100c3fffbc592ba79f3abebfe#diff-b706c6ec71f1314215d25bf1fcec7c08R21
IPv4 only environments stopped working.
Some of the configurations has been fixed in T2339.
But the fix is based on the check of the local-host option only and does not address the client mode (local-host cannot be used in the client mode, must have remote-host configured instead).
Diagnostics is the same as in T2339:
Jun 03 19:13:39 vyos openvpn-vtun0: RESOLVE: Cannot resolve host address: x.x.x.x:1195 (Address family for hostname not supported)
Setting openvpn['protocol_real'] to 'udp' would apparently fix the issue.
If IPv6 protocols need to be set by default, remote-host could be also checked when in client mode to configure IPv4 protocols.