We have run a simple test to see if linen fabric will catch fire just because of lantern standing under it.
As you will see we arranged quite extreme condtiions. The distance between the lantern and canvas was very little but it was done on purpose to speed up the test. However, once we were witnesses of burning tent that caught a fire from lantern standing about 1 meter under sloped canvas wall.
It took less then 25 minutes for standard canvas to catch fire in such conditions.