Don’t listen to what anything on the internet tells you about .ai and .ar top level domains not being compatible with DNSSEC. They actually are and they each use the older RSA/SHA-256 algorithm. This was discovered when a user routinely imported a .ai domain name on Namecheap into ENS despite documentation across the web saying it would not be possible for this tld. Importing was doubly confirmed when I imported a .ai domain myself. However, since so many registrars are under the assumption that DNSSEC is not possible for them, Namecheap is the only registrar I’m aware of so far that will activate it for these domains.
DNSSEC compatibility can be determined using this tool published by Verisign Labs. It’s how I determined that .ar also uses DNSSEC despite registrars attesting the opposite. If you’re uncertain if a domain name can use DNSSEC, especially given the amount of misinformation surrounding DNSSEC across the web, use the tool to double check.
For the record, Namecheap will not host .ar domains so you’d have to find a registrar that not only accepts that tld, but also realizes that DNSSEC actually does work on them.