I could help to port the mod to 1.16 as I already saw that you are working on it.
Where could I start contributing?

Hi UV, when the mod was ported to 1.12.2 I pretty much had to comment out most of the code. What is currently in the 1.16.5 branch is mostly block stubs until they can be implemented fully. Many of them will depend on a resource loading system I was working on that I haven't completed yet. For now I'm working on block events and then probably slope rendering and collision code before moving on to anything else. After that, I plan on attempting to resolve the resource loading and then work on the Flower Pot. Then, it's going to be a grind converting 1.7.10 render code to the new system.

The only other block that doesn't depend on anything unfinished is the Collapsible Block, which I think had a basic implementation in 1.12.2. I haven't checked what's broken there in 1.16.5.

But, feel free to contribute wherever you're comfortable.