Dan113841: Nevermind. Got it running smoothly by tweaking dosbox frame skip settings.
Steam Deck is a nightmare for editing text config files if you don't have an external bluetooth keyboard, I can tell you. Whose bloody idea was it to include a sophomoric emoji button on the onscreen keyboard and not a ctrl, alt or esc key?
Are you using GOG's DOSbox or DosBox staging? Because the game will look kilometers better in Staging with the configuration reconfigured.