Semi-related, since SDL added support for DOS a few weeks ago I've worked with Claude to port Cave Story to DOS [1].

On a Pentium 75 it can get 30fps and with decoupling the frame timer it plays at the same speed as the original. The port offloads the Organya synth soundtrack to MIDI to improve performance, and also sounds amazing.

Still working on a few bug fixes, performance tweaks, and Waveblaster support, but it's playable.

1. https://codeberg.org/ecliptik/doskutsu