How do you come up with/discover the personas?

You talk to people! Something that's a lot harder for a FOSS project to arrange. User Experience (UX) is a whole job, including interviews with users. And a related job is Service Designer.

"Design thinking" is a good starting point to Google😉

This is a rambling tangent but one of my super weird memories from the late 90s was being asked to a market research focus group where all they did was give us cell phones and sim cards and video us trying to open the backs and insert the sims. It was new tech for most of us at the time and it's really funny to me now how challenging we found it.

That market research group sounds like the above UX stuff I was talking about!

SIM card swapping is an interesting line of thought. Because you could sell phones with them installed, so problem solved. But if it's hard to do, you might struggle to convert customers from a competitor. But at the same time, it might help prevent your customers leaving.

Do you know what they were trying to learn?