Currently there is no Big Sur device driver available for the Prolific based USB Dongles.
MacOS Big Sur has FTDI based devices supported by in-built Apple device driver. The USB dongle requires a device driver, which with MacOS Big Sur need to be 'notorised' (signed) to work.
These are sold under various brands but most are based on either: To allow newer USB equiped computers to talk to RS-232 based devices you need a USB to RS-232 dongle. Nowaday's pretty much every desktop, notebook and server computer have USB ports and RS-232 ports are only on either specialist or older devices. USB 1.0 was introduced in 1995 and is now in its forth generation with USB4, which means USB is now over 25 years old. So for those of you who still have the need for RS-232 Communications and use Apple Macintosh computers here is the Big Sur low down. The latest 'thing' to break with MacOS are some USB to RS-232 Serial Communications dongle drivers. Status: Updated May 2021 - Big Sur 11.2.3 - Tested with ATEN (Prolific PL2303) and FTDI RS232R USB Dongles
