Monstera has crispy brown leaf edges but the soil is never dry Light and Water

Permanently damp soil in a plastic pot with bagged compost is the actual problem, and the brown edges are the symptom of roots that cannot drink rather than a plant that has not been offered water. Compost that stays wet for three weeks is compacted and has no air in it, roots suffocate, damaged roots cannot move water to the leaf margins, and the margins die first because they are furthest from the stem. Take it out of the pot and look: healthy monstera roots are firm and pale, bad ones are brown, soft and smell sour. If they are bad, cut them off, repot into something chunky with bark and perlite mixed through, and water thoroughly but only when the mix is nearly dry throughout.

Worth ruling out the boring cause too: mineral or fertiliser buildup gives exactly this papery edge, especially if you have hard tap water and never water enough to run out the bottom. Flushing with three pot volumes of water once fixed it for two of mine.

40 percent humidity is not the villain here despite what every plant account claims. Monsteras do fine in ordinary flats. Chasing humidity with a spray bottle is the most common way people avoid dealing with a root problem.

New leaves unfurling with brown tips is the detail that makes this a root or salt issue rather than an old-damage issue. Damage from a past mistake stays on old leaves; new leaves report on current conditions.

A plastic pot is fine but check it actually has open drainage holes and is not sitting in a cover pot with 2cm of water in the bottom. I have found the second one more times than I would like to admit, in my own home.