I don’t think the supplied remote sends any IR commands; they’re all RF.
(Well, I assume the ones that can turn on the TV and control the volume on other devices use IR, although even they might use HDMI-CEC. However, for sure, most of the UPC TV box commands are sent using RF.)
If you have, or know someone who has, a Logitech Harmony remote they can send most (but not all) commands to the UPC TV box using IR. Then you could use that remote to program yours.
I’ve just googled, and you need the “Pro” version of your Broadlink thing to get RF capabilities. How that’s programmed, I don’t know. I’d not even heard of Broadlink remotes but they do look interesting! Going to research …