Thanks a lot for all the answers.
Let me reformulate the problem. I'm developing a game (on my Windows computer). It's not a commercial game, it's just for fun. But I'd like to send it to my friends so that they can play it. The problem is some of them have a Mac, so I cannot send them the Windows executable.
The reason why I asked for MSDOS is that I have a good experience with DOSBox. I'm using it to play old games, and it works perfectly on Windows, macOS, and Linux. So if AGS could build an MS-DOS executable would be a fantastic solution in terms of portability (DOSBox is also used by gog.com to distribute games commercially). I mean, if I play Monkey Island on DOSBox, I don't see why I could not play my AGS game. But I can understand start to code for MS-DOS in 2021 is insane.
Wrapping the Windows EXE in Wine would have been possible, but starting from Catalina, it doesn't work anymore, plus it's not a good solution (a wrapper can be more than 1GB for a game that is just 10MB). It's ugly.
ScummVM can be a good idea. I like that. With a ScummVM build, the game would be portable to all platforms.
An even better solution would be an HTML5 build. This way games would be playable on the web, which would be awesome. At least it's a new technology, not like MS-DOS, but I have no idea how complex would be to have an HTML5 build in addition to the Windows EXE build.
Said that, thanks a lot to the developers of AGS, because it's an amazing tool. I'm actually having a lot of fun developing my game.