Canon MF4350d with 10.15.7

The question should be does Canon still support this printer in macOS Catalina.

It is up to Canon to provide the necessary drivers and software for their product on

differing operating system platforms.

The first thing to do is go to the Canon support page for your printer,

https://www.canon.co.uk/support/consumer_products/products/fax__multifunctionals/laser/laserbase_mf_series/i-sensys_mf4350d.html?type=drivers&language=en&os=macos%2010.15%20(catalina)

Make sure the operating system selector is set for macOS 10.15 Catalina.

Yes the printer is still supported there a various downloads for your printer,

scroll down the page and download them. Now install them.

Restart your mac.

If there is any problems with the printers functioning then you can try

Reset the Mac printing system to solve a problem - Apple Support