TLDR: better get a modern Xperia device than the Gemini.
I have one for about a year, which I initially bought to program and tweak on as it seems to me to be easier with a keyboard than the touchscreen.
The device is nice to tinker and try stuff on SFOS, but it’s too big/bulky to carry every day, and with no
Android app support can’t realistically be a main device (unless you have basic phone needs).
But at the end, I’m using it quite rarely, as the touch terminal on other SFOS devices is good enough for a few commands, and I’m on my computer for all programming stuff (so SSH to device).
The SFOS experience specifically is as SFOS gets on any of its supported devices, but some apps won’t rotate correctly. Other than that, it’s just plain old normal SFOS.
I would say, it’s better to have an Xperia 10 II over the Gemini (or the future III), and play with it. It’ll be more versatile, the license covers Android support, aarch64, and you can use it as an everyday smartphone when needed.