There are some apps (like Intra) which allow you to connect to a built-in (cloudflare, google) or custom DoH server (your own or other providers which support DoH).

Nextdns have their own app for this as well.

For android 9 or higher there should be an option in network settings.

Right, I specifically use DoH with Cloudflare on my phone. I'm talking about the "we don't need this" reply above, which is a suggestion for tinkerers, not a good recommendation for general population.

VPN if that isn't blocked or throttled by your carrier?

Though you need a trusted host to act as the other end, or you are just swapping one monitored link with another, and finding that could be a task in its own right depending on your threat model / paranoia level.