I was just doing some browsing and stumbled upon this company, Badaptor. They make adaptors to mix and match brand batteries for use with Ryobi tools. I was interested in a possible Ryobi product, but already started committing to the Ridgid ecosystem. So this might be a nice accessory to have.
Website:
https://badaptor.com/us/
Interestingly, they don't list a Ridgid->Ryobi adaptor on their official site. I did find one on ebay that might have been an older product:
https://www.ebay.com/itm/274601236269. However I did snoop FB and Badaptor said the Ridgid->Ryobi adaptor should be officially launching in the summer.