Well, the easy and fast answer to your need is : “install BeePi “ which is already optimized for RPI3 (see link in my signature)
But as BeePi also include Aranym and a complete Mint OS, it could be too much for you. It’s up to you.
Now, if you want to build Hatari to run on a Pi, it’s kind of tricky, as SDL2 by default is build to run on X only and is not accelerated. As a result, Hatari will be slow like hell (1-2 FPS) and unusable. If you build Hatari with SDL 1.2 on the over hand, it runs at a decent speed under the console frame-buffer, but can’t scale the output full screen.
You have 2 solutions :
1 : use SDL 1.2 and decrease the console resolution to 640x480 and let your monitor do the scaling
2 : build SDL2 for the frame-buffer accelerated dispmanx driver (good luck!) or easier, scavenge a SDL2 build from RetroPie which is already built for the dispmanx https://files.retropie.org.uk/binaries/ ... _armhf.deb
Regarding using Hatari with midi on a RPI3, it works but not very well. I have done only quick tests, but every time the synchronization was chaotic . The same version of Hatari on a X86 was working perfectly, so I am afraid that the RPI3 may be to slow for midi emulation. But as I said, I have not done deep tests, so it could also come from an incompatibility of my midi usb interface and Raspbian, or a bad optimization.