How do I ensure that ProtonVPN use it's own private DNS on Android?

VPN
1

What configuration should I use on the “private DNS” setting? Automatic or Disabled?

2

Keep “private DNS” off and check here that Protons DNS goes thru there servers

https://dnscheck.tools/

3

You can read more here:

https://protonvpn.com/blog/private-dns/

4

That didn’t answer my question, it just mentions browsers. Should I default to “disabled” or automatic" in the private DNS setting on Android?

5

I’ve got off, automatic and custom. With the Proton VPN client, I’d suggest going with Off to let Proton use their own.

A different story would be using the wireguard client with specific rules and a custom DNS as NextDNS.