This is true. And it’s also why I always recommend downloading steam through their website. They distribute their own Deb directly, and it auto updates.
Flatpak version is also okay but if you want to use a secondary disk then you need to know how to use portals (or the Flatpak configuration tool that I can’t remember the name of).
Since it sounds like this is your home router since you mentioned you use Comcast. If you are testing the site from within your network using your external ip then you are possibly running into a loop back block. Comcast does not allow traffic that originates from within your network back into your network.
Try the ip/site from a Hotspot and that might work.