As per title, this would be the minimally viable ping as designed in bug 1790569 and would plug into the existing infrastructure, possibly here where we send the legacy ping.

Glean-based crash pings are sent alongside legacy crash pings.

Depends on D166925

As we are planning to support Firefox on Android as well, should the glean pings/metrics be added to the gecko_{pings,metrics} categories rather than firefox_desktop_{pings,metrics}? Or should we keep it as firefox_desktop until we support Android too?

Chiming in to say: It's safe to do either of the options you propose. Putting them in gecko_* will just create some empty tables until we start sending things from Fenix. Putting them in firefox_desktop_* and then moving them later is supported by our infra.

Fenix is the next logical step so we can start with gecko_*. The main driver behind this is having telemetry from Fenix too. History note: we used to have fully-featured crash pings back when Firefox for Android was Fennec, however they were lost during the transition to GeckoView.

That was my thought exactly, I've already made the change locally. I've just been waiting for data review to complete before sending the new patches.

https://hg.mozilla.org/mozilla-central/rev/ff31f4ed8cfb