There are several, in fact.
RFC8375 [0] states:
> This document registers the domain 'home.arpa.' as a special-use domain name [RFC6761] [1] ... 'home.arpa.' is intended to be the correct domain for uses like the one described for '.home' in [RFC7788] [2]: local name service in residential homenets.
In addition to "home.arpa.", there are several other domain names listed in IANA's "Special-Use Domain Names" registry [3] that "users are free to use ... as they would any other domain names" -- even if they are technically intended/reserved for other uses.
For as long as I can remember, I've used a subdomain of one of my registered domain names for everything in my home network. That has the advantage of, if and/or when desired, allowing me to do some "fancy tricks" (involving some combintion of DNS, VPN, and/or reverse proxying) to make specific internal/private resources available from the Internet.
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[0]: https://tools.ietf.org/html/rfc8375
[1]: https://tools.ietf.org/html/rfc6761
[2]: https://tools.ietf.org/html/rfc7788
[3]: https://www.iana.org/assignments/special-use-domain-names/sp...