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So I'm brand spanking new to the RPI world and just picked up a new PI 3 B+, and am trying to get Ubuntu Mate (UBM) onto it. I downloaded the Pi version from https://ubuntu-mate.org/download/, formatted the SDCard as FAT32, then wrote the UBM image onto it, stuck it in the Pi and plugged the power cord in. Now all I get is this screen (note the lightning bolt at the top right).
I've read that the lightning bolt means the power adapter isn't giving the pi enough power, but, using the same cord I didn't get any lightning bolt, or power issues when running the normal Raspbian. I also installed KDE Desktop on Raspbian, and though it ran dog slow, I never got any 'underpowered' notices...
I also tried re-writing the image 3 separate times just to be sure I didn't get a 'bad write'; once in Windows using Win32 Disk Imager, once in Windows using RaWrite, and once in Kubuntu using ddrescue, all resulting in the same screen above.
Anyone have any ideas what's going on?
NOTE: Though the "possible duplicate" linked is very similar, and has some very useful, similarly related info, it's not an exact duplicate of my question. The linked question is asking how to get older Pi 3B sdcards/firmware working on the newer Pi 3B+.