compatible printer

Maybe. HP suggests using their App to set it up, but their App requires 10.14 Mojave or later so won't download on High Sierra.

You may be able to plug it on over USB and get it to show up in System Preferences->Printers & Scanners.

It does not however appear to be AirPrint compatible here: About AirPrint - Apple Support

So may not work wirelessly without drivers which HP does not seem to offer for it for High Sierra. https://support.hp.com/us-en/printer-setup/hp-officejet-pro-6970-all-in-one-printer-series/8289585/model/11161264

Hi,

As Phil0124 indicated, the 6978 model is not listed in the About AirPrint article (only an HP OfficeJet 6970 All-In-One). The HP specifications at https://support.hp.com/us-en/product/hp-officejet-pro-6970-all-in-one-printer-series/8289585/document/c05061732 include the 6978 model, though, and AirPrint is mentioned under Mobile printing solutions. So, one should perhaps not completely rule out the possibility of using AirPrint.

Generally speaking, an AirPrint-enabled printer is compatible with macOS 10.13 High Sierra (AirPrint as such can be used with systems as low as Mac OS X 10.7 Lion), and should be possible to use without additional drivers, provided that the printer and the computer are connected to the same network (Wi-Fi router).

However, a printer manufacturer may supply special software with higher system requirements (such software could be intended for setup, ink management, and similar purposes). That alone should not make it impossible to use a printer with an earlier system, but the software may be needed in case of certain ink subscription offers. Without a special setup app, one could investigate whether a fully manual setup would work (via Wi-Fi Protected Setup, a printer's control panel or embedded web server, et cetera).

http://h10032.www1.hp.com/ctg/Manual/c05139126.pdf