I installed Ubuntu 20.04 on my MacBook Pro today with a USB and went through the installation process during which I chose to remove OSX and just have Ubuntu on the machine.
After this it all worked fine, I started setting it up and downloading apps etc. then at one point closed my laptop to go do something else. When I came back it had turned off and when I tried to turn it back on by holding the power button it booted to the splash screen and stayed stuck on that for a while with the spinning wheel spinning infinitely:
I left it for about ten minutes with no progress and when I do CTRL-ALT-T to open the terminal, the text shows up but nothing moves and no new commands come in.
I turned it off and on again multiple times to get the same result.
Eventually I plugged the USB with the .iso on it again and booted it up which took me back to the installation process (although now my trackpad wouldn't work). I didn't want to go through this again as I figured it still wouldn't boot after I closed the laptop again.
I just tried holding ALT while powering up which takes me to the screen where I can select the EFI drive:
After selecting this, a black screen appears with the message "System BootOrder not found. Initializing defaults." It then took me to the login screen with my user profile I set up earlier, but my trackpad wasn't working. I could try plugging in a USB mouse and going from there, figuring out how to install the drivers to allow my trackpad to work, but clearly this is going to happen every time I boot up.
I'm completely new to this so have no idea what to do, my guess is that there is something I have to do after installation is complete to set up future boot processes but I don't know how to do that.
I am on a 2017 MacBook Pro with 2.3 GHz i5 and 8GB of RAM. It's [this one] here.
Please let me know if you need any more information. Thanks.