Is USCIS accepting the paper filing of I-539 or do we need to file extension online?

Hi Anil,

My Mom is in the USA and her I-94 expiry is on August 4th. Due to COVID situations am planning to apply for an extension of stay.
I have a quick question:

Is USCIS accepting the paper filing of I-539 or do we need to file extension online?

USCIS is accepting both online and paper application.