How can I mirror Android phone screen to pc wirelessly or via usb without root

I ran into the same frustration with Phone Link on my S24 - it's hit or miss with screen mirroring depending on the device. Since you have an S25 Ultra and need something that works reliably without root, Screentrol might be worth checking out. It's a Windows app that uses scrcpy under the hood but wraps it in a simple GUI so you just download and connect, no command line needed. Works over both USB and WiFi, and the USB connection gives you basically zero lag which sounds perfect for your app demos. The fact that it also includes zoom functionality is a nice bonus that Phone Link doesn't offer.