[pkscout]

Actually, I just did another pass, first removing another plugin I tried before (Visualization Plugin), then enabling both Show Fanart player setting, and AS did work! The quality is not great (it's dark and low contrast), but at least it's working now. Also, it looks like it is cutting top and bottom of the vertical images (so it is fitting the width only). I kind of remember these issues were discussed on this forum before, I'll check my old notes.

Glad to hear it's working now.  The dark part is the skin.  Estuary by default puts a black image with some transparency in front of the image so that any writing that comes up is legible.  The skin by default also assumes the images are 16x9 ratio, so vertical images especially will get cut off  For the second issue you can deselect the option in AS to dwonload images regardless of resolution. Then it will download only 16x9 images.  You'd have to go through and delete any already downloaded images that are not 16x9.

The other thing you could do (which is a bit more work) is to download my Estuary mod.  Among other things it eliminates the dark overlay (as long as you aren't showing the info like the song/artist info and album artwork) and has an option (in the skin settings) to not try and scale images AS downloads.  There's a link in my signature to the thread for that mod, and that thread has instructions for downloading my skin repo so you can install the skin.

One last thing.  If you've left the AS storage set to the default of Kodi addon_data folder, you might want to turn on the option (in the storage section of the AS settings) to limit the size of the download cache.  Your TV probably has limited local storage, so purging older artwork (which will be downloaded again later if needed) might not be a bad idea.  If you set it to a custom location and used something like an SMB share, then you're probably fine.