I bought a Pixel 9 Pro Xl specifically to use with GrapheneOS. Unfortunately, its OLED and my eyes were incompatible. The PWM on the screen was terrible and I had to return it after some headaches.
Of course, none of that was the fault of GrapheneOS. I absolutely loved using it and think your project is vital.
Ahaha, don't get your hopes up, friend. The possibility of an adequate, degoogled Android with picky requirements as GOS on good, ultramobile hardware (matte DCI-P3 IPS, 3.5 mm audio, USB-C 3.2 or better, dedicated, ideally quick-access mSD card slot, IP68 rating, good cameras, EMR pen compatibility, changeable battery, non-plastic case) is virtually nil. That would essentially be a modern hybrid between a Samsung XCover Pro 6 and one of the older Samsung Note phones, e. g. the Note 9. Days long gone... :(