There are some reserved suffixes, including .localhost and .test: https://iyware.com/dont-use-dev-for-development/.
Not sure if that is important for the use-case at hand, but it was the reason why I stopped using .localhost in my LAN (in favor of just using plain hostnames, e.g. “x1”).
There are some reserved suffixes, including .localhost and .test: https://iyware.com/dont-use-dev-for-development/.