Rant:
If you let people install the software easily, they'll just pirate and won't buy the software. If you lock things down you'll irritate people and they won't buy the software. If you make it open source they'll just build it themselves and won't buy the software. If you make it open source with a license that restricts commercial use (or is even too copyleft e.g. AGPL) people will bash you for having a "non-free license" and won't buy the software.
There's really only one method that's working broadly: SaaS. The cloud is the ultimate DRM. You don't even give people the binaries or their own data. You keep it in the cloud and charge rent.
SaaS works. People won't buy software that they can run themselves, but they'll rent it and give up all privacy and control of their own data.
SaaS even lets you pretend to be open source by "supporting open source" (tossing a few bucks in sponsorships or employing one or two open source authors) or having an open source client for a closed source SaaS platform. Nobody seems to care about that. They just look at the license on the source, not the holistic picture of the ecosystem that it works within. At the same time you can build your SaaS on the shoulders of open source, using all those dumb hippies as free labor.
I love making software but I absolutely despise the way this market works. It's completely perverse.
It's hard to make money in software by doing things to make peoples' lives better or increase their freedom. It's easy to make money with rent extraction schemes, addictionware, dark patterns, and outright scams. It's like this market is full of people who want to be screwed and refuse to pay for anything that doesn't screw them.
The reality is that we painted ourselves into a corner with free-as-in-beer, "information wants to be free," etc. without considering how incentives work in large systems. You get what you incentivize. By making anything that is pro-user and pro-human free (as in beer) and educating the customer base to expect it to be free, you remove all incentive and resource base for the development of that kind of software. The only incentives left are for things that make the world a worse place. The best way to make money is to con, dark-pattern, lock in, addict, surveil, or outright scam the user.
I've spent years trying to build useful software. I'm not doing too bad. I've somehow made it work. But with the same knowledge that underlies my current work (cryptography, distributed systems, network protocols, infosec) I could have become incredibly rich scamming people in cryptocurrency or doing dozens of other shady-but-not-illegal (or illegal-but-hard-to-prosecute) things.
Half the time I'm proud of not doing those things. The other half the time I feel like a big fat sucker.