First, let's get some terms straight. SDRUno is a SDR application, not the SDR itself. Unless we hear otherwise, we can assume you are using a SDRPlay SDR (which one is not relevant to this discussion).
Yes a transmatch (often mis-named an antenna tuner) might help in some situations, particularly if you are trying to use a less than optimal antenna (or to make something work on frequencies it was otherwise not designed for). As mentioned it's really not a requirement.
It is better to put the antenna up and away from the house (where there is a plethoria of noise causing devices) as much as practical.
Loops generally don't need to be high - in fact, keeping them closer to the ground is an advantage if you are using it on MW frequencies and lower, where you can use its directional properties to null out interfering stations.
Instead of just googling the subject, our wiki has several things that might be helpful. That being said, probably the 2 most popular antennas would have to be the PAR EF-SWL and the W6LVP loop (with Wellbrooks and the Pixel in that mix, too, though they're much more expensive). MFJ also has a receive loop that is popular. Check these 2 articles (links are always in blue) for links....
wiki.radioreference.com
wiki.radioreference.com
Mike
