Future-proofing top-level domains for private networks

I recently installed some new servers on my home network to discover that systemd-resolved doesn't resolve hostnames without dots. This got me on a journey on the internet trying to find what is the best practice for choosing a TLD for a private network and future-proof it. To summon it up: there is no possibility to be sure of this. In the early age, during the 90s, the Internet was more a playground for everyone. Then, in the end of the 90s, commercialism took a good grip over the Internet, it's future and over the TLDs. After reading this: https://www.theregister.com/2018/02/12/icann_corp_home_mail_gtlds it is obvious that we will never be sure. The private IP-ranges (10.0.0.0/8, 172.16.0.0/12, 192.168.0.0/16) that will never see the day of light on the public Internet is really common knowledge and regarded as a fact. But concerning TLDs for private networks, there seems to be a lot of confusion . Some of the camps and sources for them are: 1) Never use private TLD - buy a domain! 2) According to https://www.rfc-editor.org/rfc/rfc2606 these are the only valid ones: .test, .example, .invalid, .localhost 3) Here https://www.rfc-editor.org/rfc/rfc6762#appendix-G they advocate to not use private TLDs at all, but if you must, choose one of these: .intranet, .internal, .private, .corp, .home, .lan 4) According to https://en.wikipedia.org/wiki/ISO_3166-1_alpha-2#User-assigned_code_elements there are some 2 character TLDs that can be used for private networks. Please read an active draft from ICANN on this subject: https://datatracker.ietf.org/doc/html/draft-ietf-dnsop-private-use-tld-00 5) Some suggests using .[0-9] as a private TLD because it is not valid according to RFC-3696 and therefore will never be delegated by ICANN. See: https://cr.yp.to/djbdns/dot-local.html As you can see, for example choosing .home as your private local network TLD could be a gamble. Maybe ICANN will drop it for commercial purposes, maybe not. Questions that comes to mind are: why don't we have a plethora of TLDs for private networks? Is it because there is no money for ICANN in this? Is it because there is no advocate for private users there? Of course this is a reflection of where the main body of people come from that are engaged in these organizations: the universities, the commercial sector and the government. Question: what would be the best mature path to take in this matter? ::: UPDATED WITH CONCLUSIONS ::: After further readings on this subject and looking at the answers and discussions on SE and elsewhere, I have come to the conclusion that these are the future-proof TLDs for private networks: - AA, QM to QZ, XA to XZ, and ZZ - [0-9]{1,}