Dual monitor with 1 hdmi port, 4 usb ports and 1 ethernet

@snapplekid123  The reason the HDMI devices you're finding only mirror is because HDMI ports do not support running multiple independent displays from a single output.  Only DisplayPort can do that, as well as USB-C because USB-C uses DisplayPort for video output.  Unfortunately you didn't specify what system model you have (always a good idea when asking for technical assistance/advice, for future reference), but if you're sure that HDMI is your only video output, then your only option would be what I wrote in the first reply in this thread -- but be aware of the drawbacks that I described in another thread I linked to over there.  Are you sure you don't have a USB-C port that supports video output?  If so, then a USB-C to HDMI cable would be a much better option.  (Note: Even if you have a USB-C port, not all of them support video output, so check that.  Here again it would have been useful to specify your system model, since in that case I could have just looked up its specs.)

@speedstep  That adapter is fairly outdated since it only supports up to 2048x1152.  The nearest resolution to 2048x1152 that's actually used by today's displays would be 1920x1080.  There are multiple adapters on the market now that support up to 1440p or even up to 4K 60 Hz and that are roughly the same price -- and I already linked to those in the thread I suggested that the OP read.  Some of those adapters are made by Plugable, which you mentioned (as did I in the thread I linked).

And Speedstep, Plugable isn't limited to 6 displays, in fact they aren't the source of any limitations to begin with.  Limitations would come from DisplayLink, which makes the chipset and software that Plugable, J-Create, and other vendors rely on for their products.  DisplayLink used to have a limit of 6 displays, but that was removed a long time ago.  Here is an article and video from Plugable showing them running 14 DisplayLink-connected displays.  And that article is from more than 6 years ago.  So as in many other cases on this forum, your information is incorrect, in this case because it's very outdated.  And then there's the fact that the OP only wanted to connect ONE additional display, so the information about maximum number of displays was completely irrelevant anyway.  But if you're going to post irrelevant information, it should at least be accurate and current.  (In fairness, DisplayLink itself still claims 6 maximum displays, for reasons explained in this thread, but that isn't a hard limit.  And in any case, you didn't mention DisplayLink's information.  You were talking about Plugable, and they clearly went past 6 displays years ago.)