Welcome
I have pihole installed on ubuntu 20.04, external ip server vps 15.15.147.58/32
I also have an openvpn client installed on the same server which receives the address 10.8.0.10/24
I installed pihole and chose the option to work only on the tun0 interface.
On the laptop I also connect as an openvpn client and enter the DNS address 10.8.0.10 or in the browser http://10.8.0.10
Everything works fine. Pihole server I work properly.
Unfortunately, after 12 hours from starting the server, the server stops working, I can't connect to it or via ssh via ip 15.15.147.58
After another server restarations for 12-13h everything works fine and then internet on vps stops working
I connected to the VPS server using the KVM console and noticed that when I issue the netplan try command and then click enter, the internet starts working.
I noticed the difference in the result of the ip a command when the internet is working
inet 15.15.147.58/32 scope global dynamic eth0
whereas if the internet does not work then I have
inet 15.15.147.58/32 brd 15.15.147.58 scope global eth0