The classic procedure remains the same for Blender versions prior to 4.x: download normally and place the add-ons in the correct folder. (I might look into creating an add-on for versions that don't officially support this simplicity.)
I've shared my modifications to stk-website; you can modify it or use it as inspiration. For updates, simply regenerate the zip files with Blender, replace the zip files on the site and the JSON (if the original hasn't been deleted XD), and adjust the YAML file as needed.
Blender versions 4.x and above will automatically update their local JSON data for the website, and users will only need to download updates in Blender.