Note: this one is mostly generated by ChatGPT, but I didn't check the correctness, saved just in case, for future use. Here we basically have compiled sources and run a make install to install them inside the gonna-be flatpak package.
A manifest.yml file that specifies package dependencies and build instructions.
app-id: org.example.myapp
runtime: org.gnome.Platform
runtime-version: 3.38
sdk: org.gnome.Sdk
command: myapp
build-options:
install-commands:
- make install
modules:
- name: myapp
buildsystem: simple
sources:
# specifies the files that flatpak will be built from. May be omitted if the `build-options`
# refers to a prebuilt directory or archive through `install-dir` option. In this case
# `install-commands` should be omitted as well.
- type: dir
path: .
Then to build the flatpak package:
flatpak-builder /destination/directory /path/to/manifest