When I installed Endeavour OS today, it asked me to find a mirror. Due to the resolution of my monitor (32" Westinghouse TV HDMI connected to Lenovo ThinkPad T430), the box to select countries did not scroll to the bottom, or rather, the bottom was off the bottom of the screen. I could not resize the window nor could I move it to where the bottom could get higher. Since the UK and US and other U countries were off the bottom of my screen, I could not effectively select a new country.
Eventually I solved the problem by increasing the resolution of my monitor. I should not have had to do that. I keep it at 720p because of poor eyesight (ditto for why I have a 32" monitor).
I can probably provide a screenshot of that if you need it.