I am attempting to setup Rust+ on my server, and am having issues with it showing up on the mobile app.
I have referenced this rust wiki, but still am having issues.

Currenlty, I am attempting to use the default port of 28082. Through port checking tools, I am able to see that the port is OPEN for the server's public IP.

When using the app.info command, the listening IP matches the public IP and port that the port checker says is open.
What other steps need to be done in order to get the Rust+ app to show my server?

It's going to be 67 ports up from whatever your server port is. I have two servers:

1st server:

server port 28020

query port 28021

rcon port 28022

2nd server:

server port 28023

query port 28024

rcon port 28025

For Rust+ app, I opened all ports 67 above the 6. So ports 28087-28092 are opened for TCP. UDP isn't needed and shouldn't be set. Use the tool mentioned in their wiki and make sure you don't remove the compainion.id file.