Don’t use arpa.
in-addr.arpa is reserved for reverse dns.
Pick something else.
I’ll add that I am aware of the RFC from 2018 regarding home.arpa, that doesn’t change my advice. It’s not worth the trouble trying to MacGyver this.
Please read again: arpa or in-addr.arpa are something different (except sharing same technical TLD).
home.arpa is exactly for local network configurations and private home networks, where a public domain is not desired - you already provided the RFC. Hence “Pick something else” might not be a good advice, as DNS requests have risk of being routed to public otherwise.