Compile on older container to get binary that runs on older OS too (SDL doesn't compile on older than 20.04):
docker run -v .:/SDLRousku -it --rm ubuntu:20.04
  On Linux, install the packages listed at
  https://github.com/libsdl-org/SDL/blob/main/docs/README-linux.md#build-dependencies

in addition apt install xdd nasm libwayland-dev

mkdir vendored
cd vendored
git clone https://github.com/libsdl-org/SDL.git
cd SDL
cmake -S . -B build -DBUILD_SHARED_LIBS=OFF
cmake --build build

git clone https://github.com/libsdl-org/SDL_image.git
cd SDL_image/external
./download.sh
cd ..
cmake -S . -B build -DBUILD_SHARED_LIBS=OFF -DSDLIMAGE_VENDORED=ON -DCMAKE_PREFIX_PATH=../SDL/build
cmake --build build

git clone https://github.com/libsdl-org/SDL_ttf.git
cd SDL_ttf/external/
./download.sh
cd ..
cmake -S . -B build -DBUILD_SHARED_LIBS=OFF -DSDLTTF_VENDORED=ON  -DCMAKE_PREFIX_PATH=../SDL/build
cmake --build build



AppImage:
make install DESTDIR=AppDir
appimage-builder