IOS Is there a way to lock out "DNS/Automatic"

Hello The only way I found was to use IVPN and use NextDNS for the custom DNS a setting within IVPN and on disconnect there is an option when disconnected from IVPN I use NextDNS again another built in rule. I think it’s the only VPN out there that has it built into the VPN itself  but I did stop looking for other solutions since finding IVPN.
Maybe other solutions out there for you that I don’t know of. Not sure if this can help you for what you are trying to accomplish but NextDNS is always on and the DNS setting doesn’t change to auto on iOS on my iPhone anymore as IVPN settings takes over all DNS requests from NextDNS no matter what happens when having the custom rule & on disconnect rule enabled for NextDNS it will never shutoff unless I hit the anti tracker switch (quick disable for DNS rules as the two can’t work together)  or if I disable those 2 DNS rules for NextDNS.There is a 1.3 second delay when reconnecting to the VPN but hard to say if the disconnect rule takes the same amount of time, as I can see my ISP making 2-4 connections in the NextDNS logs when reconnecting to the VPN It quickly reconnects and I never shut the VPN off but just encase you see your ISP if using the VPN that will be the reason when switching it on or changing location.

Good luck