On Testnet3 I checked on testnet.ordinals.com, but for Testnet4 I can't find equivalent.
Maybe one of websites listed on
Want info on RARE SATOSHIS, RARE SATS? Casey Rodarmor? Read, Learn, Get Started support testnet4.
OK, now I know that I asked this question in the wrong place. Although I thought I would find answers to the most difficult questions related to Bitcoin here.
FWIW while Ordinals and similar stuff deployed on Bitcoin network, it's not part of Bitcoin protocol itself.