DisplayPort to HDMI adapters (such as the CAC-1056, CAC-1070, CAC-2070, CAC-1080, CAC-1085) only work in one direction (DisplayPort output of computer to HDMI input of display). To connect HDMI output of computer to DisplayPort input of display, you need a HDMI to DisplayPort adapter (such as the CAC-1330, CAC-2330, CAC-1331, CAC-1332)
Only DisplayPort output can do MST. HDMI to DisplayPort adapters cannot do MST to multiple displays.
The specs for the HP Pavilion Gaming Notebook with a Nvidia GTX 1660 Ti at
https://store.hp.com/CanadaStore/Merch/Product.aspx?id=10M27UA&opt=ABL&sel=NTB says it has the following:
1 SuperSpeed USB Type-C® 10Gbps signaling rate (USB Power Delivery, DisplayPort™ 1.4, HP Sleep and Charge)
So what you need is a USB-C to DisplayPort adapter (such as the CAC-1507, CAC-1567). For your laptop which supports DisplayPort 1.4, I would choose the CAC-1567. Then you can connect your MST Hub to that. For higher refresh rates and resolutions, replace the DisplayPort 1.2 MST Hub with a DisplayPort 1.4 MST Hub (such as the CSV-7300 or CSV-1550).
I’m not sure if displays connected to the USB-C or HDMI ports of the laptop are connected to Nvidia or Intel graphics – check the Device Manager.
I don’t think there’s anywhere in Windows that shows the MST Hub. But the graphics drivers will be able to show multiple displays when connected to the MST Hub. If a MST hub is connected to Intel Graphics, then the Intel Graphics Control Panel can show the topology.
Linux has the fwupdtool command that can list MST hubs that use a Synaptics chip. The Linux dev directory can list the DisplayPort Aux channels of each DisplayPort port (for MST hubs, you need a display connected for the device to appear).