When I was looking around the fantasy computers, I found one that was configurable. It had presets for different popular machines. I saved the link and closed the rest but when I was about to start I realised I saved the wrong one and I haven't been able to find it again. Did I just dream it? The one I started on instead was tic-80.

You can kinda skirt some of the limitations with Pico-8's multi-cart feature. It gives you more storage space via a simulated cartridge swapping system.