Made good progress over the weekend!
First, I was able to get frame buffer in DRAM on STM32F429 DISCOVER board. (The real board will use F469, that has enough SRAM.) With that I finally can run frame buffer with the full VGA resolution and 30 lines by 80 columns cell display. It turned out to be somewhat slower than using the SRAM, but this is just a prototype. With that in place, I updated the font to use awesome 8x16 Terminus, which has great number of Unicode code points for both normal and bold styles. HTOP and Midnight Commander look real now:
Also did more work on XTerm compatibility and I can now edit ASCII terminal source code on ASCII terminal. Self-hosting achieved!
Last, but not least, SETUP interface is now in good shape. And invoked by the classic Ctrl+Alt+Del sequence.