Did you try enabling the exploit protection compatibility mode in the app settings? GrapheneOS should have shown you a Play Integrity API detection notification if the app is actively trying to block non-GMS-certified devices using Play Integrity API.
This is a correct answer despite the fact that it was previously hidden by flagging. PayPal's recent updates with incorrect anti-tampering code work fine on GrapheneOS when secure app spawning is disabled. It's best to disable only secure app spawning (exec-based spawning) for it instead of using the whole compatibility mode. Using the whole compatibility mode is the first thing to check before narrowing it down though.
So the OP is just lying out of ignorance and rash judgement, and spreading calumny about PayPal. And PayPal has done nothing to their app to block GrapheneOS. And hundreds, thousands of participants on HN have been misled by another rogue "Tell HN". Good times.
They're not lying but rather likely didn't know about the per-app exploit protection compatibility mode. They narrowed it down to secure app spawning needing to be disabled. Now they know what to do when an app doesn't work on GrapheneOS.
You can help by upvoting the update they posted with the solution:
They did actually and knowingly lie. Because I guarantee that they had no way to affirmatively know that PayPal themselves had done anything to their code. They didn't see no ChangeLog and they didn't see no Release Notes about it. They didn't read any news from the app developers. They jumped to conclusions about malice when it was actually incompetence and ignorance, much like their own.
They could've simply neutrally stated that: "PayPal crashes when I try and run it under GrapheneOS" and that would be a true statement without assigning blame or malice. But, not knowing PayPal was innocence, they chose to assign malice to them instead. That's a choice. That is rash judgement and calumny.
