For experimental, I have now removed the release as it will remain on 0.2.0 until experimental becomes the new stable version of Factorio. The mod portal is not supporting such updated ZIP files and generating a new release for the sake of only having the mod portal "see" a new release isn't really helpful and will pollute changelog.txg with tons of bumped version for mod portal only "changes".

So when you want to play experimental (2.1), please git clone the github repository into your mods directory and keep it updated with git pull and git checkout experimental-2.1. The full clone command might be this:

For AR-core: (needed!)
git clone https://github.com/Quix0r/AbandonedRuins.git --branch experimental-2.1

For AR-base: (optional but recommended for having some generic ruins spawned)
git clone https://github.com/Quix0r/AbandonedRuins-base.git --branch experimental-2.1

It clones the GIT repository and then immediately checks out the experimental branch. So a seperate git checkout experimental-2.1 isn't needed. After that you should continue (perhaps not daily) try a git pull on both AR-base and AR-core repositories.

You CAN also try the downloadable ZIP files at github but keep in mind to update them manually by checking yourself if something has changed. As might have guessed already, this is not recommended as you might miss updates. Best (and recommended) way to stay up-to-date in 2.1 is the GIT command way.

So 2.1 is supported by this mod but only through GIT repository.