Since I have tried it myself yesterday, I can confirm that the Web installer failed on ym Surface Pro 11th edition. My Pixel 9 Pro was recognized, and I was also able to unlock the bootloader. Flashing the firmware also worked, but it got stuck when flashing the system. I used the Edge browser.
Luckily, I had my work laptop at hand as well and could continue the installation in Chrome on Windows 10, where copying and flashing GrapheneOS worked like a charm.