SRT/RTMP to OBS Source from Larix Broadcaster

Hey there! So I've read about 20 forum posts dating from 2015 to now which all have people asking the question "How do I use RTMP as a source for OBS" and most of them are looking to either: 1) Collect one or more RTMP sources on their local network and use them as a source on OBS or 2) Set up OBS to stream to an RTMP server.
My case is a little different.
I'm looking to use the Larix Broadcaster app on multiple phones to broadcast over the cellular network (4G in this case) and collect those sources on a singular PC. So no local network sources. The implementation is for local car racing, where we will be streaming the race to a twitch channel. We have cameras which will be recording the race, but we'd love to see some in car footage (don't mind a delay) and if people would like to broadcast that to us it'd be nice to say "Here's the info you enter in to Larix" and we can just quickly add that as a source.
Now, I've been trying to get remote RTMP/SRT streams to work but I can't for the life of me figure out what's going on. I've port forwarded in my router the port I'd like to accept 1 stream on, and set up everything in Larix as far as I can tell the right way with the info I'm reading but I htink I'm reading it wrong as I can't get them to C O N N E C T.
I've made a diagram, I hope it helps, and any help and advice would be super helpful, thanks!

A little late maybe, but I'm doing the same thing.
I got it working, but my problem is I can't get it to work using 4G and my phone as a hotspot, and that's why I started googling..
However it does work for me over the internet if I use a regular wifi connected to cable/fiber.
I'm pretty sure it's my Android phone that is the problem, even though I've allowed the Larix Broadcaster to use cell phone network (4G).

Maybe you have the same problem?

I'm also missing some information in your diagram: Do you have a RTMP server setup on your PC accepting the incoming connection?
I'm using NGINX as described here: https://www.youtube.com/watch?v=n-EdUHNK9UI&ab_channel=DougJohnsonProductions
(Nevermind the part about VIDIU, it's the NGINX part you need.)

TLDR; I've successfully setup this except from I can't get my Android phone to stream over 4G.

Please let me know if you have had the same problem and know how to fix it, or if you have any other questions :)