I have a PC that has Ubuntu 20.04 on it only. I don't want to dual boot with any other OS.

I have a Debian 10 ISO flashed to a USB stick and when I boot from this stick it shows me the Debian launcher. When I click "Install Debian" it just ignores it and boots right into Ubuntu.

So Ubuntu is just booting right past my Debian USB stick. Would anyone know why that is? Does Ubuntu have some sort of fast boot I need to turn off? This isn't happening on another PC I have windows on, it boots into the installer GUI.

Any help would be appreciated!

so you don't want dual boot, but want to install a different distro. I guess you need to give us more info. What is put on the stick exactly, what's happened exactly. (in general it should work).

dftag,

Welcome to LQ forums.

This is a strange one.

Have you tapped the appropriate boot key (F2, F12 etc) and then selected, say, SanDisk for your Debian flash drive?

There may be more than one choice such as USB HDD UEFI or USB HDD.

Are you using UEFI or Legacy/CSM boot?

What is the full name of the debian iso your using? How did you flash it to the usb? What is computer model/specs?

If you don't already know, you need to set your computer to boot from external media before internal disk.