Plug your phone into the pc and choose to trust the PC. This should share your mobile internet with your PC
I use it all the time, when I distrohop on my laptop with a wifi card that needs to download b43 from the internet before WiFi works 🤪
Definitely unplug existing router, else you may end up with a doubleNAT… I have a physical opnsense (without wifi antenna) plugged between my IPS router which in modem mode and another proprietary router which acts as bridge and wifi access point.