Started making the extension for Appodeal SDK, it is here:
It’s on the very early stage, so I wouldn’t recommend to use it yet!
Though at this point the SDK can be already initialized (with forced Interstitial and Rewarded ad slots) and can show interstitial ads. Works only for Android yet.
Update: the extension now supports interstitial and rewarded ads with the necessary callbacks. Android only
Update: iOS target works, interstitial and rewarded ads only. The setup process is a bit complicated, still need to add the frameworks downloading/unpacking script (similar to what AdMob extension has) and the docs to explain the setup process.