Had to be reminded of putting device in Fastboot mode. Stupid me. Lately playing around with too many meshtastic devices and esp32's which don't need that while flashing. As it's my first device running GrapheneOS and not my main device (iPhone17Pro (private) and a simcard-less SE2022 (work for authenticators) I can play around with alpha, beta and stable versions. Managed to set it to Alpha. Getting to know GOS. 2 profiles.. Private (main) and Work. The latter has the sandboxed Google Play Store. Running Wireguard to my private GL-iNet Slate7 VPN server.
I was amazed how seamless the web install was, even after my initial screwup.
I understand that the warning from Google about the firmware at booting/rebooting is something I can not turn off. So be it.