Yes, you can be an LSP by just running some software -- and it is profitable to do so.

The first time I wrote LSP software was probably Swap Service which lets you do what Boltz Exchange does except you make the money instead of them. More recently, I revised that code and released Zaplocker, which is partly the same thing, but it also has new features e.g. it works for lightning addresses and lets people have a non-custodial one without needing to run a node. (Zeus Pay runs an instance of zaplocker software as well, though Evan rewrote the codebase because my code is bad.)

One of my goals is to make third party intermediaries unnecessary. Another of my goals is to make them as widely available as possible. Those might seem contradictory, but I don't see it that way. Some people want to use third parties for some services, and that's fine, but I'd like that to be an option rather than a need. For those who want third party services, even non-custodial ones like zaplocker come with some risks, such as being deplatformed, but these risks are mitigated if everyone can run a copy of that same third party service. So, making LSP software serves the latter goal: let anyone be an LSP, let a thousand flowers bloom, make it profitable for anyone who wants to give it a try, and that helps LSPs in general evade regulatory capture.