I recently bought a car, and could not find one without a cellular modem and microphones. Removing the modem voids the warranty. The period where you can opt out is mostly over.
For the manufacturer to avoid a warranty claim due to a modification or aftermarket part, they must show that the defect was linked to the part or modification.
They might have to show that it was caused by, but in any case, if your paint fails prematurely, they can’t say your warranty is void because you disabled the cell connection.
Otherwise it is probably mostly equal to driving without registration. It may not be a felony, but it will be fined.