CUPS didn’t work for me as I can’t see an upload option on the web UI.

And you won’t. For the purpose of printing, CUPS is a print server, not a web front-end. It facilitates communication between client devices and downstream printers.

Printing is implemented through IPP, which is an HTTP-based protocol. You have to add the URL of the printer as it appears on the web UI (e.g. https://print.mydomain.net/printers/PRINTER_NAME) as a printer in the client device’s printer manager. It’s plug-and-play on Linux and Mac, and needs a driver (even if it’s the generic PostScript driver) on Windows.