I recall getting that No Route To Host error when the network I was connecting to used the same IP scheme as the one I was currently on.
For example, my home network and my wife's clinic network were both 192.168.86.x. And I couldn't VPN into her VPN server from home, but it would work from elsewhere.
So I change my IP scheme at home to 192.168.80.x (it was less painful).
I'm using OpenVPN on a CentOS VM at 3 locations (home, in-laws, clinic).
Some info I recall having to mess with to get it to work:
On my VPN server, the /etc/resolve.conf is:
search lan
nameserver 192.168.80.1 [the router address at the VPN server's location]
And some lines from my /etc/openvpn/server.conf:
#push "dhcp-option DNS xxx.xxx.xxx.xxx" [I commented this line out]
push "dhcp-option DNS 192.168.80.1" [the router at the server's location]
push "redirect-gateway def1 bypass-dhcp"
push "route 192.168.80.0 255.255.255.0" [the network addresses at the server's location]
push "route 10.1.1.0 255.255.255.0" [the antlets' network range]
I emphasize in the file above that the 192.168.80.x stuff is the DHCP info on the VPN server's network.
Also, when I VPN to a location, I have to add .lan to the end of device names [example: I RDP to RECEPTION.lan, not RECEPTION]
Also also: To get the VPN service to even come up, I had to add this to the XML config for the vpn antlet (virsh -c lxc:/// edit {antletName})
<hostdev mode='capabilities' type='misc'>
<source>
<char>/dev/net/tun</char>
</source>
</hostdev>
per this site:
https://www.redhat.com/archives/libvirt-users/2018-January/msg00075.html