How do I edit the hosts file of an iPhone?

You don't have to if you use mDNS. Or configure the iPhone to use your own self-hosted DNS server which can just be your router/gateway pointed to 9.9.9.9 / 1.1.1.1 / 8.8.8.8 with a few custom entries. You would need to jailbreak your iPhone to edit the hosts file.

I have a real domain name for my house. I have a few publicly available services and those are listed in public DNS. For local services, I add them to my local DNS server. For ephemeral and low importance stuff (e.g. printers) mDNS works great.

For things like Home Assistant I use the following subdomain structure, so that my password manager does the right thing:

  service.myhouse.tld
  local.service.myhouse.tld

Exactly, you don't. My qualm was with the "hosts file works well enough" claim of the person I responded to.

This is what i do.

> Just giving them hostnames is easier

Bitwarden annoyingly ignores subdomains by default. Enabling per-sudomain credential matching is a global toggle, which breaks autocomplete on other online service that allow you to login across multiple subdomains.

Tell me about it... that infinite Ctrl + Shift + L sequence circling through all credentials from all subdomains. Then you brain betrays you making you skip the right credential... ugh, now you'll circle the entire set again. Annoying.

You can override the matching method on an individual basis though, just using the setting button next to the URL entry field.

Seriously? That sounds incredibly awful - my keepass setup has dozens of domain customizations, there's no way in hell you could apply any rule across the entire internet.

You can set that globally but override at the individual entry.