Bought: January 2020 from store.google.com/ for 350 pounds.
Front camera video on Android 11: about 100MiB / minute. The encoding is however super inefficient, a FFmpeg re-encode without any options reduces it by 1/3.
For Fastboot mode: Power and Volume down simultaneously for 10-15s. It is OK if screen sleeps. On "no command", power then volume up to see options.
2023-10: touchscreen not registering touches anymore. Still displays images. Manage to regain access with wired USB mouse + a simple USB-C adapter. RIP. Will attempt replacement: store.ifixit.co.uk/products/google-pixel-3a-screen-genuine?variant=42388954448071, partly to get Authy access which I had never properly tested... Replaced screen, but at exact same status as before: shows image but no touch. thus I wasted my money and time (minus the learning) something else is broken.