I've been experiencing some actual content crashes but even if I forcibly crash a content process, the crashes don't show up in about:crashes. Nothing in my profile's minidumps directory, either.

(Note: my profile does contain 2 crashes from when I was trying an emulated x86 build on this ARM64 laptop so those do show up in about:crashes so about:crashes isn't entirely non-functional)

You're seeing bug 1526276. I'm investigating it but it's hard to run a regression because the build was broken for a few consecutive days.

Thanks and good luck!