I unfortunately do not know how to interpret the information provided by nyanmisaka there.
Does "GT 710 doesn't support NVENC" mean that adding the older GPU wouldn't do anything to provide a performance boost to the server? Or only for videos encoded in a specific way? I.e. is there any point in keeping my passively-cooled GT710 in my server or should I just ditch it?
What do you think would be the minimum entry-point to adding a GPU then? I'm reluctant to adding a full sized double/triple-fan current gen GPU to the server because I don't want to increase its idle draw beyond reason.
a 1050ti is what i got. I managed to find mine on ebay for ~50 moneys but it took some looking. If your price range is higher I have heard good things about intel arc and they are one of the cheaper ways to get av1. You may not even need hw accel if it is just for one to two people. I don't use my card (yet, it doesn't fit in the case) and my i7 4790 handles 1080 just fine with software.