Just had to mess around with this some more.
the fancy app-style RISC OS renderer runs under aemulor.
Finally, after much hacking, got the 2sprite converter to run under aemulor...
it seems to have RGB ordering issues. I know this is sort of a thing under RISC OS on Raspberry Pi. Some part of the system wants, like, GBR or something, but it's never bitten me before so I'd have to rtfm to even talk about it correctly.
"I appreciate SDF but it's a general-purpose server and the name doesn't make it obvious that it's about art." - Eugen Rochko