Same lack of text printing using Big Sur on my 2015 12" MacBook (Retina). I've attempted to print text files from FileMaker Pro 18 Advanced, as well as from LibreOffice 6.4.6.2. to my Canon Imagewriter MF4350d. This was not a problem with the prior Catalina OS, although Catalina disabled my ability to send email via the Apple Mail application. Replacing Catalina with Big Sur fixed the email problem, but unfortunately also introduced the printing problem. I've tried the fixes listed here and elsewhere (i.e. deleting and re-loading up-to-date Canon print and FAX drivers) with no discernible results; a print job is sent to the printer over WiFi, but only blank pages are produced. I also replaced my toner cartridge, and of course that did not alter the outcome. The problem clearly is a Big Sur OS bug that Apple should have identified and corrected by now. This is not an obscure or relatively minor problem; we still live in a world that at times requires paper documents. In my case, I have to produce a report for a court case that occurs two days from now; my low-tech fix for the moment is to send the document to my office email address, ride my bike to my office (a mere 12 miles) Come on Apple, you can do better than this!