Needing a (simple) solution for adding license server activation to my game?

I have developed a few tools and games using Unity and have been allowing some users to freely test the betas for the last two years. I have found a small community that has been extremely helpful and very positive which has allowed me to continue developing. I now have a new version of my game that is almost ready for release with added features and functionality. Currently my project is freeware but I would like to begin asking for user's support via subscriptions or one-time perpetual license purchases. Also I would like to attempt to raise funding using Kickstarter and offer my game to a wider audience.

However at this time my game runs as stand alone without user accounts or log in management, so anyone who possess the build my easily unlock all features or share the game without restriction.

Does Unity (2019) include any features or license servers that allow controlled distribution?
My game current has no multiplayer functionality.

I am very unfamiliar with Steam, are they the only platform for Unity games?

Also I have some experience in developing REST and Django web frameworks, should I just build my own simple license server/database and web frontend? I am uncertain if building a DIY license server would be perceived as "unprofessional" though.

Are there any basic approaches or tools that I may implement so I may securely distribute my game to registered users?

 

Unity doesn't itself include a licensing server. This is typically handled by the distribution platform (Steam, Play Store, App Store, Epic Store, etc, etc).

I like Steam because after you're all set up you can both charge for your game on the store as usual and still provide free keys to select people you want to try your game.

 

It is not handled by the distribution platform, they only provide you with the tools. Some platforms like steam do have an automated DRM wrapper, but the steam DRM wrapper doesn't work with C#/.Net which means you have to implement it manually, which is luckily pretty easy, but if you don't implement it then users could just copy your steam game and run it on other computers.