You can prevent this by adding a credit card to your account. It “upgrades” your status, and then as long as you stay in the free tier allocations you won’t be charged.

I currently use a custom filter/rewrite in AdGuard Home (similar to pihole).

An alternative to running a central dns server is to use mDNS. You can install a daemon on each server that you want to access via hostname, and then clients know that ServerName.local domains should be resolved using mdns. They send out a dns query to a local multicast IP, the daemon on the servers receives the query and the appropriate one responds. By design it’s local only.

I read somewhere that Lemmy.ml has basically maxed out its VPS with its provider, so they’re stuck for the time being, whereas Lemmy.world actually just upgraded its server hardware. Hoping they’ll migrate to a beefier server soon.