They have officially stated that they can support the 10 now, but it will have to wait until after the port to QPR1. https://xcancel.com/GrapheneOS/status/1960792610114511190#m

That device didn’t meet the requirements for GrapheneOS even when it was supported by the OEM. As of now, it is an EOL device and is highly insecure. https://grapheneos.org/faq#future-devices

LineageOS also significantly regresses security compared to barebones AOSP.

• Userdebug builds
• No locked bootloader or verified boot
• Incomplete backports of patches