I've been working on my MSXdev entry that'll reuse my adventure game engine, but it uses multiple memory pages, one page per episode (of which there are three). So a bit of a hack rather than do it smartly already the first time.
Anyway, I looked at the Wiki page. I've been using the last freeware version of tniASM (v0.45) so far. I tried copypasting the sample code there for tniASM, and it complained of stuff like "end" and "B000h". I tried fixing those (drop the "end" command, replace B000h with $B000), but... BlueMSX worked as I hoped, Webmsx and Openmsx 0.15.0 (haven't looked if there are any updates) both show just the text from segment 1.
What would you suggest I do -- contact TNI about buying the 1.0 version (I've used the freeware one for three games and a bunch of prototypes by now, so it's about time I paid for the program), have the freeware version produce working megaroms by some fix I don't know, or start using a different assembler? All my changes to the model ASM code there were to replace the 8000h -format of hexadecimals with $8000 -type and drop the "end" from the end of the file.
I'm pretty sure the last option will mean I can't partake in MSXdev'21 since I have the content for half of the game not made and little of what is done, is polished. But given the high number of entries already in the contest, my game isn't really needed there.
(I suppose I could also download another assembler, try compiling the sample rom with that, and then do a bytewise comparison of the result files to find out what I'm doing wrong...)