> .local already does this

Best to avoid it for that purpose:

1. "Using '.local' as a private top-level domain conflicts with Multicast DNS and may cause problems for users." https://www.rfc-editor.org/rfc/rfc6762#appendix-G

2. ".local has since been designated for use in link-local networking, in applications of multicast DNS (mDNS) and zero-configuration networking (zeroconf) so that DNS service may be established without local installations of conventional DNS infrastructure on local area networks." https://en.wikipedia.org/wiki/.local

3. "PSA: Don't use domain.local" https://old.reddit.com/r/sysadmin/comments/a9sfks/psa_dont_u...

4. "Why using .local as your domain name extension is a BAD idea!" https://community.veeam.com/blogs-and-podcasts-57/why-using-...