I am building my own terminal emulator on the side, not very seriously: https://git.sr.ht/~sircmpwn/scurvy

I'm not particularly interested in extending ANSI any further than, say, xterm. I do have big plans for Sway and the rest of the ecosystem, though. I am working on a GUI toolkit: https://github.com/SirCmpwn/chopsui

And I'm also thinking about pulling the TUI layout out my work on aerc2 into a standalone library: https://git.sr.ht/~sircmpwn/aerc2