HDMI splitters allow you to connect two displays to one video source. It will work no different than if you were to connect two TVs to the same DVD player.
Physical USB C ports are used for various different types of digital signals: USB, Thunderbolt, DP alt-mode, etc. And you have to look at the specifications to see what the actual specification of the USB C ports actually are.
That said. The Nitro AN515-55 series can only support one monitor natively, through its HDMI port. The USB C ports are USB ports only, and do not support Thunderbolt or DP alt-mode, and thus, do not natively carry video signals. Almost all USB C to HDMI adapters are just that, it converts the physical USB C port into a physical HDMI port, requiring the USB C port to support DP alt mode, which your laptop does not support.
If you want to use more than one external monitor with your laptop, you need to buy a USB display adapter (i.e., a usb video card), something like this: https://www.amazon.com/dp/B00H91BQ7Y/ (link to US Amazon site)
I actually had success with this brand here https://www.amazon.com/gp/product/B00H91BQ7Y
https://streamable.com/50e566
That's not a thing that HDMI can do.
Best option is to get a secondary display adapter like this one that works over USB. It won't have any graphics acceleration whatsoever and is only good for the basic Windows UI, but it'll get the job done. Alternatively you could add a graphics card to your computer.