In Raspbian, my RPi 3 is worrying me.
I changed the RAM for the GUI from 180 to 64 and rebooted. Now I see the rainbow screen, then the SHIFT for Recovery, then the OS picker (I have 2: RECALBOX and Raspbian. I choose Raspbian then saw a black screen. I tried pressing CTRL+ALT+F2 AND tried pressing all the F buttons. I have a Logitech keyboard, if that helps. I put the SD card on my iMac but the partitions were only boot, boot0, and RECOVERY. The other ones were unavailable, they were showing up in Disk Utility, but grayed out and I couldn't do anything with them. I suspect one of the grayed out ones is Raspbian because on Raspbian I have a 16GB partition and on the iMac it had one that was 16GB. I am very scared. I had to unplug it twice to restart it if it was showing the blank screen.
I did not miss a step as I have had the RPi since April 2017.