Macbook won't let me enable double-sided printing (i.e, there is NO duplex or 2-sided option where there should be)?

That print queue is installed with the AirPrint Driver. The AirPrint driver works from lots of devices, m but has NO OPTIONS specific to the model of printer.

If you want the Options, you would need to create a new print queue, and take extreme care to select the Manufacturer's driver (IF such a driver is still available) not AirPrint Driver.

You have to have Admin rights, and use the Add-a-printer dialog to add an additional print queue for that same physical Printer.

System preferences > Printers & Scanners > ...

use the Plus [+] button under the list to get the add-a-printer box:

then proceed slowly and see what Drivers it proposes. the instant default will be AirPrint, but in many cases, you can override that and choose the printer-maker's driver instead.

You can go to the mfr's website:

https://support.hp.com/us-en/drivers/selfservice/hp-color-laserjet-pro-mfp-m477-series/7326560/model/7326586

The printer has been discontinued, so it may not even include these features or it may/may not have a driver compatible with your system. The site would not even recognize my OS - it showed 10;15 even though I am on Monterey (12).

Over the years, HP sourced printers from lots of different sources, and included whatever drivers were available. Lots of different printer worked pretty well for a long time.

When Apple introduced 10.15 Catalina, Apple declared: No more 32-bit software shall run. HP faced a HUGE dilemma. They could either:

• revise Hundreds of drivers for printers for which they were not making any new sales, -OR-

• Tell everyone to use the AirPrint driver, and deal with the customer blowback of losing features like automatic duplexing.

(They mostly chose the latter.)