Is it me, or does it bear a passing similarity to a Trade Federation AAT

I thought so too, and reading up, it's based on the original design sketches for the AAT from the Phantom Menace. Nothing goes to waste in Star Wars these days.

Hey Freddy. Apologies, I haven't watched Skeleton Crew yet, but I think I need to. Is this set in 9 ABY? Saw "Era" listing "Old Republic" and was a little confused.

Also, related to your comment about original design sketches. Remember, that's how West End Games created many, if not all, of the starship classes in their RPG books! The Dreadnough was one of many designs for the Star Destroyers, and the Rebel Assault Frigate was one of the designs for the Nebulon-B Escort Frigate. A little resizing on some pics and you get a filled out fleet. I think that's where the Z-95 Headhunter came from too, as one of the designs for what could have been the X-Wing. WEG began this, and while Lucasfilm/Disney have hits and misses, it warms me a bit seeing this tradition is still going.

Yep, it's set in the same era as The Mandalorian and Ahsoka.
But I figured this tank being based on the design sketches from Phantom Menace, the design probably predated that movie, so Old Republic. (in the episode the people on At Achrann are fighting with outdated and worn equipment, so this makes sense (at least to me)).