Nicely done on the line diagrams.
Make and model modem information? Just for the record....
At this time I do not believe that the modem is a problem per se. TBD.
It appears that all works well up to and including the Wifi Access Point(s).
As I understand the line diagrams you have two Access points: 1) served by wired connection to the router, and 2) the Tracfone wireless hot spot.
Do you know what IP addresses those devices and all other devices are using?
This router:
https://support.dlink.com/resource/PRODUCTS/R32/R32_A1_Manual_v1.01(WW).pdf
Do verify that I found the applicable User Manual.
The manual is very long and detailed. And, for the moment you do not want to or need to change anything.
Start with verifying the Router's IP address. Likely the commonly used 192.168.0.1 And the router should be using the commonly used subnet mask of 255.255.255.0.
All network devices must look for and find the router at 192.168.0.1 or whatever IP address has been used for the router. The IP address can be changed by end users with administrative rights to the router's configuration menus.
The router likely has some page that lists or shows all connected network devices, their name, IP address, and MAC. I did not note any specific screens or listings - likely some admin feature needs to be clicked.
On your Windows 11 computer run "ipconfig /all" (without quotes) via the Command Prompt. Verify that the DNS Gateway is indeed the router at 192.168.0.1. (The manual refers to a simplifed "ipconfig" on physically numbered Page 146).
Overall, your task at this point is to figure out the IP addresses of all network devices. And if those IP addresses are fixed (Static) or dynamic (DHCP). Discord may be a problem because of some IP address conflict. Again, no need to change anything - just discover more details about the network.
My thought being that there is a conflict with respect to the Access Points being used.
And you can list those "Private" IP addresses.
FYI:
https://www.lifewire.com/what-is-a-public-ip-address-2625974
Do not post your public IP address (provided to the router by your ISP).