The Surface Pro experiment has worked out better than I though it would.
A few things stand out from the experience so far.
First, using 'mkusb' to create the Persistent Bootable USB Flashdrive I am using to run Linux on the Surface Pro 3 worked very well.
Second, Mint Cinnamon is preferable for running Linux on a Surface that is to be used a lot in Tablet mode, because it automatically rotates the screen orientation - once it is enabled, while Kubuntu must be changed manually each time you reorient the tablet.
There are some other observations. While Mint Cinnamon is the best for Tablet mode, KDE is adequate once I got used to the manual orientation thing.
I personally like the Plasma Desktop of Kubuntu better than the Cinnamon Desktop, but that's probably because I use Plasma on my Mint 21.2 Desktop daily.
As far as using the Surface Pro with its Microsoft Surface Keyboard/Cover as a Laptop replacement goes, it is only the battery life that lets it down.
With everything set OFF or as low as possible it is sometimes possible to eke 4 hours out of the battery - but unlikely.
That's with Bluetoofh OFF, WiFi OFF and Screen Brightness down to 5%, and avoiding running anything like watching a Video.
That said, while Windows often reports something like 10 hours at the start of a session (on either the 4/64GB Surface or the 8/256GB one), it rarely ever delivers more than 4 hours - so I can;t blame Linux.
It is pretty easy to see why Microsoft had to introduce the Surface Go into the mix.
I haven't found a way to run the Surface 3 off a power bank, but I am one of the luckly people. With two Surface tablets, I could take both with me for the day, and by saving my work and shutting down, then swapping the USB Flash drives, I could run one for 3 to 4 hours, then get another 3 to 4 out of the second Surface. With luck the first could be on charge for an hour, which is all it takes to recharge fully anyway.