The use of 'Windows Ink' on the desktop variant of Windows 10 comes in a limited way to Windows 10 Mobile here, with DrawNotes UWP, a free canvas with 'Ink' tools on which you can doodle and scribble and then save or share the result as needed.
Sketch, draw, then share! With DrawNotes, you can:
draw your own notes or sketches
share it with apps accepting images
draw on any picture!
share a picture from the Photos app to DrawNotes, draw on the picture then share it again!
save your art directly to the picture Library
resize your canvas or your picture before sharing it!
open directly your pictures in DrawNotes on Desktop!
open multiple DrawNotes windows!
on W10M, you can't take sketch notes on OneNote. With DrawNotes, you'll be able to draw and to save your sketch to OneNote using the Share button!
Here's a quick test of DrawNotes:
The default canvas size is your screen, but you can change that - see below. Tools are for felt tip, fine pencil, highlighter, eraser and - the 'Ink' bit - ruler (shown here) and protractor. Here pen gestures near the ruler's edges are constrained along the edge - similarly for the protractor. All rather impressive - I'll let you enjoy the latter for yourself as there are some surprises! (right) a wealth of functions on the '...' menu in terms of adjusting and scaling canvas size and viewport, and in terms of saving and sharing your doodlings.
Opting to share to OneNote lets you fill in title and description and then tap to 'Send'. Curiously, on my two test phones (on different OS builds) the new note didn't turn up in OneNote. Just me? Comments welcome. (right) you can doodle on a canvas of any size, with the option to scale your viewing window to match - all very intuitive, even though there's no explicit variable zoom function, possibly to keep things simple in terms of drawing at 1:1, etc.
And here it is in action on the desktop, with a promo screenshot: