Oh oh! I got a recommendation as someone who learnt how to draw from scratch using online resources only. It does however break your requirement of using something like udemy.

Brent Eviston’s course, The art and science of drawing, starts from the basics of how to draw lines and moves its way through measuring, 3d forms, contours, and then into shading and finally gesture followed by full sketches. Follow it fully and you’ll have enough experience by the end of the shading course to start working on other courses too. That latter point is the best part; the fundamentals give you the ability to know how to pick up more skills from other classes.

This is how I would work through it if I was doing from scratch

Complete the basic skills class - https://www.skillshare.com/classes/Basic-Skills-Getting-Star...

Complete dynamic mark making - https://www.skillshare.com/classes/Dynamic-Mark-Making-Drawi...

Move on to 3d forms - https://www.skillshare.com/classes/Form-Space-3D-Drawing-Per...

Contours - https://www.skillshare.com/classes/Contours-Drawing-with-Com...

Measuring and proportions (this one can be done in parallel with the 3d form class once you get to chapter 6) - https://www.skillshare.com/classes/Measuring-Proportion-Draw...

At this point you can start to work through drawabox - https://drawabox.com/ . Some people recommend this as a start, but honestly, if you are starting from scratch it can be hard to know if you are doing things right. The previous courses will give fundamentals to actually enjoy drawabox

Meanwhile, keep progressing on Brent’s courses

Fundamentals of shading - https://www.skillshare.com/classes/Shading-Fundamentals-Draw...

Shading beyond basics - https://www.skillshare.com/classes/Shading-Beyond-the-Basics...

If you have time you can pick up the figure drawing in parallel since you don’t do shading at that point.

Intro to figure drawing - https://www.skillshare.com/classes/Gesture-An-Introduction-t...

Measuring for figure drawing - https://www.skillshare.com/classes/Measuring-Proportion-for-...

Finally , volumetric figure drawing - https://www.skillshare.com/classes/Volume-Structure-Learn-th...

Notably absent from all of this is landscape drawing. Landscape drawing is a different beast depending on how you want to approach it. If you just want to sketch with a pen, the skills you pick up by the time you do the measuring and proportions class of Brent’s will be enough to let you go into any city scape and observe the area and draw. Learning how to let go of certain details and add your expression is a very individual choice so at that point, you can look out for certain artists and study their work to choose what works for you.

Also notably absent from all of this is colour. That’s because colour doesn’t matter without fundamental understanding of form and light in black and white. For this, there are many amazing courses in proko’s online library. Marco Bucci has amazing material. And if you want to do digital painting, Ahmed Aldoori has a lot of stuff.

Basically after you pick up the fundamentals, the choice of courses opens up and each course will teach something new. But without those fundamentals, the value of those classes is hard to absorb.

Feel free to mail me if you want more info or want to chat :)