My commercial made chapati becomes brittle within 12hrs

Welcome Daniel! From this article on IndiaCurry.com about storing chapatis:

Storing Chapati for up to 2 days

The Chapati may be stored in the refrigerator for up to 2 days

• Let the Chapati cool to room temperature
• Wrap a stack of six Chapati in Aluminum foil.
• Put the foil stack in a sealable plastic bag, and close the seal
• Store the Chapati bags in the refrigerator.
• To serve Chapati, heat on hot Tawa, Microwave, or in a conventional oven

Further reading in this article tells how to store them in the freezer for longer periods, up to 3 months.

Storing Chapati for up to 3 months

For a long term storage, the dough for Chapati should be kneaded with regular yogurt. The Chapati should be cooled, wrapped in Aluminum foil and frozen

Also, from other reading, the chapatis must be very soft. To end up with very soft chapatis you would knead with yogurt or milk rather than water. Another recommendation was to let the dough sit for a length of time after preparing as the dough will get softer as it rests.

I found they last longer if made with boiling instead of room temperature water. Which is not surprising since you will get far less long-stranded gluten formation this way (and since it is not leavened with yeast, you don't need any either). It seems some (but not most of the) chapati/roti recipes found on the internet also specify boiling water.

Check out this video from Stella Parks on making bagels. She says that by making a heated paste of water and flour, and then adding that to the bagel dough can make them stay fresh longer.

Perhaps this concept can be applied to chapatis.