You're right, I did not realize but I mixed several things there. Please allow me clarify what I wanted to say even though it's a bit off-topic.

In fact I was not specifically talking about Maemo, since the N900 can boot other systems and chroot. This is part of what I had in mind. But then maybe Chen's device will be capable of booting other systems too and maybe the hardware will be properly supported and functional with these putative alternatives. However I'm afraid the community might be a little less active than for the N900, the device is probably going to be a lot more niche than the N900 was and many people have moved on.

As for the default operating systems themselves, I should just have said "flexible" and not "open". But even that might be incorrect. I always loved the ergonomy of Maemo, I believe it really is at the sweet spot between a tactile smartphone OS and a desktop OS, and that's a significant part of what made it flexible to me. Flexibility in its use (in addition to the aforementioned flexibility with alternative OSes and chroot), i.e. I was not sighing if I had to open certain file types or do specific tasks with it instead of a computer, even though a computer would be best in every case, and I can't say it's the same now with more modern OSes (I even postpone email-checking and replies as much as I can while a smartphone should excel at that task).

Of course the stylus and keyboard play a great role in that feeling on the N900, but it would not work if the OS was not designed with that in mind in the first place. The TOHKBD on Sailfish did not feel the same, although Kimmoli did a great job on the software part to allow system-wide key combinations like Ctrl+C, Alt+Tab, and so on. In fact, what I missed to really reboot the N900/Maemo experience with the Jolla and TOHKBD was probably just the stylus.

I think Sailfish is a great OS, but like Harmattan, it's mostly a smartphone OS made for capacitive screens in its current form. I think the stylus on the N900 and adapted UI totally changed the ergonomy. Capacitive is ok for simple tasks, but horrible and frustrating for anything that requires:

1. faster actions,
2. numerous consecutive or repetitive actions,
3. accuracy,
4. no obstruction of the display.

There is just no way using your finger can be more efficient than a stylus when it comes to quickly reaching distant points on the screen without being inaccurate, without moving your whole hand and wrist, and without obstructing the display most of the time. Capacitive styluses don't really make a difference, first because they don't feel the same, but also because capacitive means the OS is likely not designed and optimized for stylus use. Interactive areas of the screen are just not sized or located the same way, and the trade-offs inevitably compromise something else.

Just to illustrate in other words how I personally feel the gap between using fingers on a good OS optimized for capacitive screens and using a stylus on an OS optimized for it: using a stylus feels like using a mouse on a laptop, I can quickly cover every area of the screen with very small and yet accurate moves of just two fingers (against each other, so they are also more stable), whereas using fingers all the time for every application you can imagine, even tasks that can't be optimized for capacitive touch, feels like being left with no alternatives to a touchpad for filling a spreadsheet without Tab or Return keys. And don't get me wrong, touchpads are great for what they are, a very portable and well integrated replacement for the mouse. But really, filling a spreadsheet with no Tab or Return keys, and just a touchpad?