Historically, the best example of going it alone without display hardware, was t...

Historically, the best example of going it alone without display hardware, was the ZX80.

VIDEO comes out of the block of gates roughly center of the schematic.

SYNC comes out of the gates on the center right.

and of course the ZX81 merged the logic chips into one ULA.

There exists a kit to go the other way for a ZX Spectrum to split the ULA logic out into discrete chips again.