It would be nice indeed. Novena had that: https://www.crowdsupply.com/sutajio-kosagi/novena

So a tablet with a Bluetooth keyboard and mouse? Of course this runs into the problem that most tablets ship with horrible phone type OSes that make it hard to be productive.

There are third party Surface keyboards / "type covers" which are similarly detachable but run over bluetooth (because the Surface connector is proprietary I suppose). I have no clue about the quality but if you want it to work detached, you surely have some options.

I really want a device with the same form-factor as an iPad Pro with a Magic Keyboard but running Linux. Or even running MacOS rather than iPadOS. The cantilever design raises the screen up so much more nicely than a notebook form-factor.

The cantilever design is indeed an elegant solution, though it can make it a little more difficult to hit the top row of keys.

I was thinking that this laptop is kind of like a Pi 400 + battery + screen. If we look at is this way, then what the OP wanted is kind of already available - you can buy portable computer monitors.

Interestingly, the Pi 400 + screen is kind of a "smart" keyboard combined with a "dumb" monitor, while the iPad Pro + Magic Keyboard is a kind of "dumb" keyboard combined with a "smart" monitor. It seems like both approaches have advantages and disadvantages.

Not exactly what you're talking about, but I've seen a few RaspberryPi + iPad + External Keyboard setups where they either use the iPad as an external display or VNC into the Pi from the iPad. IIRC you can power the Pi via USB C -> PoE on iPads with sensible ports on them, so you don't need an external battery or UPS.

Again, not what you actually want (I share your pain/longing), but damn if it isn't starting to get close.

Honestly this is my dream as well. The iPad Pro has a gorgeous 120Hz Display, the most powerful ultra mobile CPU and is incredibly light. I have hidden hopes that Asahi Linux will offer a path if a new exploit is discovered.

Maybe the Pine Tab? Although it runs Linux well but not fast.

It looks like that is a tablet? The problem with tablets is that they have glossy screens. Not well suited for work under suboptimal lightning conditions like cafes.

Also its only 10". I would like 13".

Why not use a external keyboard? A cute little mechanical isn't only a eye catcher peace but also light and kinda mobile.