I flashed the Ubuntu iso onto my USB, booted into it and now a purple screen is happening. Picture linked: https://imgur.com/HLjxMMj
It seems the boot process is stuck at some point. Potential culprits are often graphic drivers. Maybe you can use the recovery mode (if that's available when booting from USB). Alternatively, press the Esc-key to see what is going on in the background. Or you can try CTRL-ALT-T to open a terminal for obtaining further information.