Just found out there is a way to launch sonic mania via retroarch
!!!maybe you also need to setup a working wii system nand/menu in retroarch can´t say for sure!!!
so long you know how dolphins works in retroarch
and how to make advanced changes to dolphins settings in retroarchs user folder
here are the basics
- get the Sonic Mania Wii port (decomp)
- make an sd image via dolphin standalone and edit the RA dolphin config
- runs via the homebrew channel .wad file with dolphin