I normally stick to clip studio on windows, but it doesn't work on linux, and windows won't be supported for very much longer
I try Krita, and I think probably I can mostly work with it maybe, sans a few conveniences(pen button and mouse drag for adjust brush size, right click to sample layer, in general editing brush properties, all I don't know how to make work yet)
but I cannot seem to rotate the canvas via gesture at all. Is there a way to make this work? two finger pan is inconvenient but usable, but without rotate, gesture falls apart and I cannot use it.

No, canvas rotating with a touch gesture hasn't been implemented.

The manual is a great help for learning how to operate krita: https://docs.krita.org/en/

Press and hold the Shift key then drag your stylus on the canvas to adjust brush size.
Press and hold the Ctrl key to get a colour picker and click/touch the canvas to pick a colour from the canvas.

The Brush Editor has very many facilities for changing the characteristics and behaviour of the brush. It's the icon on the toolbar that looks like the brush you're using.

Press and hold the spacebar to drag-pan the canvas.
Right click the canvas to get the pop-up palette then grab the black dot at the top to move it around the palette to drag-rotate the canvas.