The fact that some root stores/browsers don't trust some CAs is actually quite common. There will be some cross-sign from another CA that is trusted in Firefox in this case.
Stuff like this is quite common; we published a paper on this recently if you are interested in details: https://arxiv.org/abs/2009.08772
If you are interested in tcpdump and use it for debugging, you might potentially also be interested in the Bro network monitoring system (http://bro.org).
It gives you very deep visibility in the supported protocols, dumps easy to parse log-files by default (see e.g. https://www.bro.org/sphinx-git/httpmonitor/index.html for HTTP information) - and it is fully scriptable.
(It is actually not emscripten -- it uses a z-machine emulator I adapted to js a long time ago to run the z-machine version of star trek. But - should be good enough :) )
It's the official status of green card holders.