One of my computers is an HP Elitebook X360 1040 G8 (convertible) and I'm happy to report that in Laptop Mode both LM21 and LM22 work perfectly. There's full control of the normal hardware including the touch screen, good performance, and good battery life.
With a couple of exceptions Mint also handles the shift to tablet mode pretty damn well. The keyboard and trackpad are disabled, the keyboard backlight shuts off, and the screen easily changes orientation with rotation.
The exceptions though are so fundamental to touch screen use in general though that I feel like I must be missing something?!
First and foremost is an on screen keyboard. I know it can be enabled under accessibility settings but when I do that it splashes up a keyboard that permanently fills half the screen. If I close the keyboard window it goes away but I can't find a way to get it to come back except to unfold the machine and re-enable it again.
It may not be possible to make it launch predicatively, although Gnome itself does. but why isn't there an icon at the top or bottom of the screen that I can tap to bring it back on demand?
The second one is scrolling, especially in Firefox. I know that Grab and Drag is possible because you can do it with the regular Firefox scroll bar but the scroll bar can be difficult to get on because of it's size and even then the scrolling action is backwards of both iOS and Android. This should be fixable be enabling gestures but surprisingly gestures don't have any assignable scroll functionality.
I'm really confused by these two issues. They seem so fundamental to how a touchscreen is used, especially the on screen keyboard, that it seems impossible they weren't addressed year ago. It's far more probably that I'm missing something obvious, but what?
Figures, 30 seconds after I type all of that I figure how the On Screen Keyboard is supposed to work.
At least for me I had to enable the keyboard while in Tablet Mode and then I got a bunch of other options, including the size and layout of the keyboard as well as a "launch when needed" option. I swear, sometimes these things hide themselves from me just so I'll get frustrated.
I still looking for how to change the scrolling in FF though.
To get touch scrolling to work in FF you need to be using wayland. I had the same issue on my Surface pro.
I ended up switching to Gnome, then Plasma for this as Mint did not have any Wayland support at the time.