Test of Marlin 2.0.x - Good Results
I have a Kossel printer that uses a Re-ARM board with RAMPS and a Viki 2 display. Although Smoothieware performed well in all of my prints I didn't like the lack of LCD menu options. I started investigating the status of Marlin 2.0 and it seemed that Re-ARM was functional and the Viki2 pinouts were correct.
Sure enough, after two days of figuring out Atoms PlatformIO for compiling and getting my configuration files dialed in I was able to compile a Firmware.bin and successfully flash to my Re-ARM board. Marlin 2.0 booted right up and my Viki2 display was working. The only thing I had to change was the contrast ratio of the display. Luckily there's a menu option for contrast and it was a quick fix.
I tested G33 Delta calibration which worked great. I tested G33 P2 which also worked perfect. I did not get a chance to test UBL...at least yet. I did have an issue saving to EEPROM from the LCD. It seemed to corrupt my EEPROM, but saving from a terminal with M500 worked fine. I haven't characterized this much so I can't comment.
My only complaint was the learning curve of PlatformIO. I learned that the PlatformIO.ini file is your "Project" and that you need to edit the file to set the platform your compiling for, and that your Fimware.bin file gets spit out into a folder called .pinoenvs under your corresponding platform folder (mine is /.pinoenvs/LPC1768).
