A alternative to fairphone would be https://www.shift.eco/en/ They want to put killswitches into their new Phone which you can preorder for 535€ https://shop.shiftphones.com/shiftphone-8.html
It won't be as secure as a Pixel with GrapheneOS. Grapheneos won't support that Phone officially.
Yes, buying an used Pixel 8 or a 8a is what I would suggest. Its sustainable and doesn't fund Google.
But their phone has some unique, inreresting features, like that Killswitches, 512 GB, expandable up to 2 TB with micro SDXC card, 12 GB LPDDR RAM, Electro-scrap positive thanks to the cooperation with our partner Closing the Loop, Designed in Germany/Falkenberg and fairly manufactured in our own factory in China , modular, easy replacement of Battery that has a standard format also used in other products from them,