Need advice using a second computer screen

I posted about using an HDMI connection to connect a Samsung computer screen to my iMac. I was going to buy a hub of some sort, but that turned out to be expensive. And I believe I would still not gain an open Thunderbolt port. But the Samsung screen has been acting up the last few days, flickering and going black. I'm considering buying a new screen, currently considering Dell P2419HC - LED Monitor - Full HD (1080P) - 24".

My questions is I really would like to free up the second Thunderbolt port on the iMac so I can use it for other devices. My audio interface is in the first port. I realize using another port could make the connection slower. And, I was told I could not use anything other than the Thunderbolt port to connect another computer screen. Is this correct? Do I have any other options? Thanks.

You can try this using your USB port:

https://www.amazon.com/USB-HDMI-Adapter-j5create-Multi-Monitor/dp/B01HIV2XR6?ref_=ast_sto_dp

And for 4k:

https://www.bestbuy.com/site/j5create-male-usb-3-0-to-female-4k-hdmi-adapter-silver/6201454.p?skuId=6201454

You can try this using your USB port:

 

https://www.amazon.com/USB-HDMI-Adapter-j5create-Multi-Monitor/dp/B01HIV2XR6?ref_=ast_sto_dp

 

And for 4k:

 

https://www.bestbuy.com/site/j5create-male-usb-3-0-to-female-4k-hdmi-adapter-silver/6201454.p?skuId=6201454

You or someone had recommended an HDMI connector in another post, but I thought it had to go to the Thunderbolt port. I could not find information that a second display could be connected to USB. Thanks for the links. I will check them out.

Update: I ordered the one from Amazon. I'll report back on the performance.