Endless Paper, Procreate, Inkscape, Paper by WeTransfer, Microsoft Whiteboard, Xournal++, Bamboo Paper, Sony Sketch, Huion Sketch, Tayasui Sketches, Charcoal, PaperColor, Auryn Ink, Plumbago, Artecture Draw, Sketch, Paint, Lorien, Sketch Club, Clover Paint, Flow by Moleskine, Craft Pro, Inks and Pens are some alternatives to Concepts.