Problem with DNS resolution when NOT connected to VPN Ubuntu 20.04

When I try to access a website it doesn't work anymore and just tells me "DNS_PROBE_POSSIBLE" unless I am connected to a VPN (Proton VPN) then the internet works fine.

After some digging around I am pretty sure it is a DNS issue but I cannot understand how to fix it.

If I am connected to the VPN and run systemd-resolve --status | grep Current I get:

Current Scopes: DNS      
Current DNS Server: 10.16.0.1
Current Scopes: none
Current Scopes: none
Current Scopes: none

But if I am not connected to the VPN then when I run the same command I get:

 Current Scopes: DNS      
 Current DNS Server: ::1
 Current Scopes: none
 Current Scopes: none
 Current Scopes: none

Also I am able to ping 8.8.8.8 but not google.com when not connected to the VPN. Any advice on how to fix this issue so I can access the internet without a VPN would be greatly appreciated.

Thank you to @matigo for putting me on track! Turns out it was an issue with ProtonVPN and its new official app.

My guess is: it crashed before I started having these issues, then when trying to reopen it and connect to it, it would throw an unknown error.

So I uninstalled the app using:

sudo apt-get autoremove protonvpn

but that didn't solve my issue, because I still had a kill-switch enabled.

So the solution was to delete all connections with pvpn- in their name when showed when running:

nmcli connection show --active

and deleting them with:

nmcli connection delete [connection name]

Source: ProtonVPN support