Qbasic works fine. Freemacs works, although when you run it for the first time it takes awhile to compile all the mint files. BCC also works.
Having tested all of the options, I think if this is just a part time thing you will occasionally do with your PicoCalc, Svar, FreeDOS, or MS-DOS 4.0 will be fine. If this is going to be what you use your PicoCalc full time, it is worth the effort to build your own MS-DOS 6.22 image.
Finally got some time to play with it… Not sure if it was confirmed in the thread above, but it doesn’t work with pelrun’s uf2loader. Flashing directly (after first flashing with the nuke uf2) worked fine though.
I haven’t yet changed the config.sys and autoexec.bat, but I’d be curious what others are doing to squeeze the most memory out of it. I didn’t get quite as much free memory as you mentioned cjstoddard, with 6.22, but it was still a good amount. (I’m using a Pico2W.) Turbo Pascal 5.5 does indeed run! I had forgotten some of my old programs had used EGA and VGA (so fancy, hehe), but the text mode programs all worked fine. I also tried a copy of Xtree Gold 4.0 from one of my ancient disk archives, and that worked great too. It’s a sort of Midnight Commander like thing. (Main problem was remembering keystrokes after all these years!)
Just for fun, I tried the CGA version of Wolf3D you posted above, but I couldn’t get the registered or the shareware version to run as they both reported not having enough memory. I confirmed they worked under DOSbox on my main machine, so I was probably just a little short on memory on the PicoCalc. QBasic ran for me too, but I haven’t spent time yet digging up some old BAS files to throw at it, really I just launched the GUI and poked around.
This is really cool though. Also nice that the PC speaker is supported!
Makes me wish I’d saved more of my old DOS stuff from back in the day. I kept some things that I pulled off floppies, but mostly didn’t start archiving things well until I was using Windows 3.1 and up. So much lived on floppies and I guess remained on them. I’ve got a couple of DOS “utility” floppy disk images that I’ll check out soon. I know they had all the various compression and encode/decode tools from the early to mid 90s, an image viewer, hex viewer/editor and some other junk. Not sure if it will be useful on the PicoCalc, but maybe interesting. 