I've been using .lan, referenced in rfc6762[1] as a good alternative to the multicast .local
> We do not recommend use of unregistered top-level
domains at all, but should network operators decide to do this, the
following top-level domains have been used on private internal
networks without the problems caused by trying to reuse ".local." for
this purpose:
0 - https://www.rfc-editor.org/rfc/rfc8375.html