phase1geo
Publish to flathub
Could you publish the app to flathub? Then it would be readily available in a whole lot of distros.
What would be required to publish the application to Flathub? I don't generally handle work around distribution of the application outside of elementary OS requirements.
Here are the app requirements: https://github.com/flathub/flathub/wiki/App-Requirements (most likely, you only need to write a manifest file, the rest of the work has already been done)
And here's how to submit to flathub: https://github.com/flathub/flathub/wiki/App-Submission#how-to-submit-an-app
Once published, GitHub actions would automatically build from every commit, and would push the released versions to flathub. I would suggest to publish to flathub because then a lot of people would be able to easily install the app (I don't have any statistics, but compared to Mint or Ubuntu or Debian, the number of people who use Elementary OS is quite few).
Alternatively, if you don't want to publish to flathub, that's fine. After I opened this issue, someone found a way to install Annotator with flatpak on any distro, without building from source.
flatpak install https://flatpak.elementary.io/repo/appstream/com.github.phase1geo.annotator.flatpakref
In case you don't want to submit to flathub, please add this command to the README. Maybe rename the existing flatpak section to Flatpak (build from source), and add this command to the Flatpak section. Let me know if you want me to do that edit and submit a pull request.