Ask HN: What tools are available for proprietary software licensing?

I'm developing a proprietary product delivered as a docker image /container. I'm looking for ways to issue licenses to those who pay for it (think product key).

Obviously, I'm in no mood to start handling encryption processes so I started looking for solutions.

I came across products like keygen, kryptolens, and netlicensing.io that offer some sort of API to validate licenses within the app, but all of these are small companies with 5-10 people that could go out of business any time and generally I don't see any "big names" there.

Am I missing something obvious here? What are the standard solutions for this?