Neo6502 is small computer with USB keyboard host and HDMI/DVI output.
Found on https://fosdem.org/2024/schedule/event/fosdem-2024-2093-neo6502-in-the-matrix-open-source-hardware-and-software-modern-retro-computer-with-software-defined-architecture/

Main page is http://cowlark.com/cowgol/
It used to support the Apollo Guidance Computer used in the Apollo spacecraft, but I had to remove the code generator while rewriting the compiler and I haven’t reworked the AGC backend.
http://cowlark.com/2019-07-20-cowgol-agc/index.html
The author also ported the Fuzix operating system to the Raspberry π pico.
http://cowlark.com/2021-02-16-fuzix-pi-pico/index.html

His tool https://github.com/davidgiven/narcissus to remap keys might be interesting too.
So is his Forth system http://cowlark.com/fforth/

cl-6502 is a Common Lisp emulator, assembler and disassembler for the MOS 6502 processor.

Lots of information about building 6502-based computers.

6502.org is a resource for people interested in building hardware or writing software for the 6502 microprocessor and its relatives.

We continually strive to remain the largest and most complete source for 6502-related information in the world. This includes everything from articles and project descriptions to schematics and source code.

Yet another emulator for the 6502 microprocessor. The site also has an interesting toy unix written in JavaScript.
One can play spacewar in the browser on http://www.masswerk.at/spacewar/ (found Wed Aug 26 16:25:57 2015) and with punch cards on
https://www.masswerk.at/keypunch/, https://www.masswerk.at/cardreader and https://www.masswerk.at/card-readpunch/ (found 2025-03-13 via https://www.tuhs.org/pipermail/coff/2025-March/002037.html and https://boingboing.net/2025/03/10/make-your-own-virtual-punchcard.html)