A plain, no-frills piece. Rockstar hasn't announced a public beta. If something claims to give you one, it is a scam.
Why this is unambiguous
Public betas aren't part of Rockstar's release pattern. They only conduct closed testing under NDA. No public beta has ever been announced for GTA 6.
If it's a 'beta' offer, it's a scam (even the polished-looking ones).