Printer for IMac27 late 2012

If the printer has built-in WiFi, it usually is an Air Printer. Go to Apple menu -> System Preferences -> Printer and use the Option key when you hit the + button to add the printer. The printer should appear as long as it is on, and on the same WiFi as the Mac. If you hook it up via USB it may also work.

This brings up the Open source drivers for printers when you hold the Option key.

My series of tips including this one each has an entry for all the printer drivers available for the OS in question:

Catalina - an upgrade guide - Apple Community

Brother laser printers are great for black and white, and for more efficient inkjets than other models. See if you can find one of the inkvestments that has the older drivers you need. If not, I also like the Canons that have more than 2 ink cartidges for color printing. Both have a long history of holding older printer drivers on their website.

You can buy literally any AirPrint-enabled printer, but to narrow down that list of over ten thousand options to a manageable few I highly recommend reading Which Printer Should I Buy? - Apple Community.

If you're still overwhelmed consider any of the options on this page: https://www.brother-usa.com/black-and-white-printers#sort=relevancy&f:connectivity=[Mobile%20Device]

If you need a personal recommendation for a specific printer I have purchased earlier versions of the "top sellers" on that page. The most inexpensive models sometimes appear on sale for less than $100. They have all been trouble-free after years of use, even with Macs older than yours.

This does not diminish the importance of addressing your specific needs as Which Printer Should I Buy? - Apple Community explains. Be sure to review it.

7256Cherrygrove wrote:

/.../ I am unable to update from Catalina 10.5.7. The iMac I have is too old for the printer I bought. /.../

Any information about the exact printer model you have bought? The reason for asking is that some manufacturers recommend the use of certain software for setup, ink management, and similar purposes (one example would be HP Smart). Sometimes, such software would have a higher system software requirement, but a workaround may be possible.

There are lot of choices at a lot of prices, because different folks want different features and different prices.

And cheap printers can be expensive to run, too.

You do absolutely want AirPrint support.

Local vendor preference is a Brother printer with AirPrint support.

See the which-printer-should-i-buy link above to help focus the choices.