N900 is legendary when it comes to utility, It's also when the smartphone manufacturers realized that providing utility doesn't result in profit as compared to black box bricks with just biannual camera upgrades for that selfie.
I'm sure there will be keyboard cases for the steam deck, We still might have to carry round a GSM radio module if we want that LTE/call/SMS.
Look into the PinePhone, it runs Linux and there are several distros. You can open the back of the phone and even swap it out with other backs that add functionality. They're working on a keyboard that looks a lot like the old Psion Series 5 keyboard. It replaces the back of the phone and turns it into a clamshell style device.
> Arch Linux
> KDE Plasma
> Will be able to install whatever they like
Is that you smartphone? The one I've been waiting for?