It appears that my MX870 is no longer supported by Canon. No scanning drivers or software are available on website for OS Catalina or Big Sur. Apple support says that 64 bit machines/OS are not compatable with 32 bit programs for Canon printers. It is very dissapointing that Canon does not seem to offer a work-around on this issue. Scanner still works on my old (2009) Macbook Pro with OS El Capitan - but not with my 2013 iMac or 2019 Macbook Pro. Printer still works very well and printer resolution is better than most new AIO machines less than $500. I suspect when I do submit to buying a new printer, Canon will not be high on the list...
Similar to same issue brought me here. Our printer still chugs away, printing very well (although sometimes I have to remove and re-add it... more regularly than I like, come to think of it) - BUT the scanner is now non-functioning. Sigh.
09/26/2023: New firmware updates are available.
08/18/2023: Canon EOS R5 C training series is released.
07/31/2023: New firmware updates are available.
05/31/2023: New firmware updates are available.
05/18/2023: New firmware updates are available.
03/30/2023: New firmware updates are available.