for sure, using a custom TLS library like uTLS helps -- need to inject that GREASE cipher selection. I have a suspicion that private residential proxies are out of budget for many outfits, or the IPs are too few and then simple rate limiting kicks in? Who do you use if you're willing to share? I've not been happy with the, uhh, questionable ethics of Luminati/BrightData in the past.

There are definitely more and more sites doing TLS/TCP/etc fingerprinting or device attestation for mobile APIs, but it's still pretty rare. I mean Twitter is trying to limit requests by IP, so definitely amateur hour over there.