Put new screen on and still unresponsive

I see this particular model has reverted to LCD display from the OLED used on most other models since the iPhone X. That means there's a possibility of backlight failure on this phone, so that's something I'd check first.

Take a flashlight and hold it up close to the screen. Can you make out an image? If so, that would tend to indicate that the backlight circuitry has failed. That failure is usually on the screen itself but can be caused by fuses blowing if the screen is plugged or unplugged with the battery connected. If that was the case you'd have to have someone experienced in microsoldering replace one or more fuse on the motherboard.

Try the flashlight test then come on back and let us know what you find.

@gruey15243 Also, is the original screen functional at all? If it still works at least as well as it used to when plugged back in, that would tend to indicate that your replacement screen has an issue and you should look into a warranty replacement.