> On your lan, you really want to be doing ".local" / ".lan" / ".home".

The "official" is home.arpa according to RFC 8375 [1]:

    Users and devices within a home network (hereafter referred to as
    "homenet") require devices and services to be identified by names
    that are unique within the boundaries of the homenet [RFC7368].  The
    naming mechanism needs to function without configuration from the
    user.  While it may be possible for a name to be delegated by an ISP,
    homenets must also function in the absence of such a delegation.
    This document reserves the name 'home.arpa.' to serve as the default
    name for this purpose, with a scope limited to each individual
    homenet.

It may be the most officially-recommended for home use, but .internal is also officially endorsed for "private-use applications" (deciding the semantics of these is left as an exercise to the reader): https://en.wikipedia.org/wiki/.internal

That is a classical "design by committee" thing.

".home" and ".lan" along with a bunch of other historic tlds are on the reserved list and cannot be registered.

Call techy people pathologically lazy but no one is going to switch to typing ".home.arpa" or ".internal". They should have stuck with the original proposal of making ".home" official, instead of sticking ".arpa" behind it. That immediately doomed the RFC.