There’s a definitive answer to this question, and you can find it in RFC 8375: use home.arpa. Never heard of it before? It wasn’t assigned as a special purpose top-level domain (spTLD) name for residential and small networks until 2018.
The home.arpa spTLD isn’t a globally unique domain name, and you can’t resolve it across the internet. It’s only meant to be used inside a small network, such as your home network. Routers and DNS servers know, [in theory,] not to forward ARPA requests they don’t understand onto the public internet.
You may have seen some suggest you use the .local spTLD instead. That is an older spTLD name used by the self-configuring Multicast DNS (mDNS) protocol (RFC 6762.) You should not configure your router or devices to use this domain name.
DNS clients may defer the resolution of .local spTLDs to the system’s mDNS resolvers instead of its DNS resolver. You can end up with domain resolution conflicts, or a situation where only some devices can resolve your domains.