In one sense the observation that Ganesa is not a dome is almost reassuring.
Since it is circular shaped and doesn't seem constrained by the existing mountain range, likely candidate processes would be impact, a sunken cryocaldera, some sort of collapsed salt-dome equivalent, or sunken diapir blob-thingy, or something really, really funky.
I see a similarity between Mabon Macula, Ganesa Macula, and Menrva:
All three have roughly circular shaped interiors
All three have a RADAR-smoother deposit in the interior region
All three have streams that appear (from the branching pattern) to enter the feature from the outside and flow towards the center (one of the streams of Mabon supposedly drains to the S; I'd hazard that two of the streams in Ganesa flow inwards (at 3 and 9 o'clock) and one might flow outwards (at 5 o'clock))
All three have a RADAR-rougher central region, with a depressed area around this point (from streamflow)
Both Menrva and Ganesa have some sort of bright RADAR alluvial outflow removed from the feature. The source of these both seem to come up from chaotic terrain.
If I had to speculate wildly, I would hazard that all three features are impact features, in various stages of relaxation/burial/erosion.
The central peak could be the remnant of a central peak crater, or it could be something pushed up from a subsurface source activated by the impact. (Like a cryo-plug dome). From the appearance (or lack thereof) of a surrounding rim, I'd further speculate that Mabon Macula is the oldest, with Gansa, then Menrva. (Menrva still shows a nice rim)
Here's a side by side comparing an image of Dilmun Crater to Ganesa Macula:
Click to view attachment-Mike