What does this have to do with GrapheneOS (compared to Lineage)? Did you reply to the wrong comment?
We don't know everything it can do
Neither do we know this about any other CPU on the market. All chipsets on the market are proprietary. All of them. And no, despite many people (who don't know anything about what they are talking about) claiming this, RISC-V won't actually solve any of these issues. Sure, the ISA is open source, but the ISA would be the worst place for malicious actors to introduce a backdoor. I can guarantee you that despite using the RISC-V ISA, the chips themselves will still be fully proprietary and the IP will be highly protected as trade secrets. You can build a fully RISC-V conformant chip with a backdoor, there's absolutely nothing in place that could stop this, and it surely won't change for the forseeable future.
Do you mind sharing which bank you use?
You can use this website to check if your banking app is supported: https://privsec.dev/posts/android/banking-applications-compatibility-with-grapheneos/
LineageOS itself drastically weakens security even compared to stock AOSP, for example by exposing root access or deploying insecure SELinux policies
Security-wise you're better off using whatever OS comes with your device (as long as it gets updates) than downgrading to LineageOS. At least most smartphone vendors (except for Fairphone) manage to ship their Stock OS with a locked bootloader and somewhat working Verified Boot.
After paying Trump millions, yeah
Yeah those are the main reasons. It's also proprietary, and the only way you to create an account/back up your stuff is by entering a phone number, which isn't exactly great for privacy.
With out bloatware and proprietary Google stuff though
Keep in mind, you don't have to be an activist or journalist to get targeted with sophisticated spyware. This very recent Lemmy post is a great example: https://slrpnk.net/post/15858999