Also is there a list of valid licenses?
There are no "valid" licenses across the online platforms of the gambling world. There can be legitimate platforms that doesn't have any license but would still pay you and fair to its customers, and there are 'licensed' (it can just be a fraud/fake license) that was just scam. But we do always consider the license of a gambling platform that is to operate in their local country. But with such license being shown publicly to all of its users, it is also important to double check it. Most countries do have a local department
(which gives the licenses to gambling/casino owners to operate) that has online websites which you can see if such companies where registered or not.