What is the GPU? Some sort of FPGA?

Edit: Also picture missing from the page, the keyboard:

https://codeberg.org/TechPaula/LT6502b/src/branch/main/Image...

Edit2: Found a few suspects in BOM: ATF1508AS-7AX100, ATmega88PA-AU, ATmega644P-20A

Would love to know what each will do!?

The previous one hints a bit: https://codeberg.org/TechPaula/LT6502

A blog entry: https://www.maddox.pro/?p=414