In the meantime, I was playing around with a dedicated GitHub repo to see if GitHub Pages could somehow simulate an alternative source (like SynoCommunity & Co.) to allow automatic package updates. Everything seems OK, but when I go to add the additional source on DSM 7.3, it goes to a blank page.
On DSM 7.2, on the other hand, it correctly detects packages.json, but it doesn't read the details contained within it properly and therefore doesn't allow me to install/update your package automatically.

I hope to be able to spend a little more time researching the problem and - possibly - the solution without going through Docker containers and the like, I was hoping to be able to do everything in an easier way (precisely, via GitHub directly, the easiest thing to automate as much as possible).