I don’t remember if I’ve shared this before but I was reminded by seeing that Clip Studio Paint can work on Linux via Wine. (Though apparently there can be difficulties and CSP can be expensive to buy outright or involve a subscription?)
If you happen to have an iPhone (even secondhand and as old as iPhone 13… which is still pretty new tbh…) you can buy Procreate Pocket for a one off of $9.99 to draw on your phone with your finger or whatever cheap stylus. Procreate for iPad is $19.99.
For Android there are free or cheap options (Reddit link).
Ibis Paint seems to be a popular option (Reddit link) for Android phone (free with in app purchases) but isn’t the only one. Apologies that I can’t find a neat list of free Android apps that are specifically for phone - even with Boolean search the search engines seem to have enshittified and I am tired.
Ps. Some might say that having an iPhone or iPad isn’t frugal.
However it might have been a gift, bought before hard times came, secondhand, a work phone, part of a family plan, a loaner, a donation from a domestic violence service, or simply bought for the functionality to do everything without buying a separate computer.
Let’s not fuss about it. I think we can all work to get the most out of what we have regardless of what it is.
I went poking around in F-Droid (an alternative app 'store' for FOSS for Android) and found an official Krita release from a couple of years ago (early 2023).
It does not have a mobile UI. Whatever UI toolkit it's built with scales nicely to my phone but it's definately not practical and/or of any use on a phone (that being said it may work fine on a more powerful phone with a stylus).
It might be better for an Android tablet though, but I don't have the hardware to check it out.
I don't know on mobile, but on desktop Krita is the Blender of art software. Superior to photoshop in many ways. Oddly i always see people suggesting Gimp, which is like a toy compared to Krita in my opinion.
My understanding is Krita started off and continues be a drawing/painting program with support for various tablets, digital pens/stylus whereas GIMP is for image manipulation (working with existing images in the vein of photoshop). I think for many people they find that they are able to accomplish most of their needs in either/or program.
Funny thing is I use Inkscape for my modest layout and design needs, even though it's a vector graphics program.
The thing is, as someone who worked with photoshop most of my life, Krita is a much more capable image manipulation software than Gimp, really comparable to photoshop. While Gimp is, to me, really more like a toy. It's entirely capable if you just need to do something basic but it will quickly show it's limitations if you need to do professional work.
I guess that may be the issue, that Krita got the stigma of being only for drawing and art. Or, what I think, is just that Gimp is more famous. And since most people don't need a professional tool, they only try that and recommend it, not even knowing that there is something better.
And finally, almost every professional uses photoshop so they don't even know about either Krita or Gimp (and the ones who tried Gimp will give up on open source alternatives quickly). While 3D had a reasonable amount of options before Blender, so people were more willing to try something else.
Just my guess... I hope Krita gets the support Blender got, because they could change the industry in my opinion if they get more funding.