Looking for very low distortion wide-angle

[Macro_Cosmos]

https://www.flickr.com/photos/133023063@N04/albums/72157674498763620
Have you considered this?
The 12mm has cutout grooves that engage mechanically with the camera to pass on aperture values; allowing all metering modes.
The distortion is near 0 at infinity. There is some at close focus, which this lens really is capable in doing:
Dominating Thistle

Pros:
Really good build quality
Small compared to other UWAs
Takes 100mm filters rather than ipad minis
Focus throw is long enough at macro distances for precise focusing
Easy to focus, dial to infinity and back a bit for landscape, done
Fast, f/2.8
Insane sharpness and resolution, even wide open

Cons:
Jerky junk hood and cap, Laowa sells an optional one for $15 or so. Get that. That also allows 95mm filters.
Horrible flare at specific angles, encountered twice when shooting normally. Easily avoidable
In general, flare control isn't that great.
Coma = bad. Doesn't improve at f/4. Really this is the only downside. Doesn't matter if one doesn't do astro. I choose to shoot 3 vertical shots and stitch the best regions

It might be too wide. Some cases, I simply find it to be too wide. Great results when used correctly, crooked if not. Lines need to be controlled... wish I own a geared tripod head.

[spraynpray]

My Friend has a Laowa 15mm f4 macro with built-in shift capability.  Because of the shift it throws a big image circle so coma isn't an issue.  Fully manual, but zero D.

[Macro_Cosmos]

My Friend has a Laowa 15mm f4 macro with built-in shift capability.  Because of the shift it throws a big image circle so coma isn't an issue.  Fully manual, but zero D.

Really? The 15mm/4 has the same distortion profile as the older samyang 14/2.8, mustache-like. It's quite horrible in terms of distortion, but it's really intended for macro where distortion doesn't really matter since we're shooting close.

FYI, the shift doesn't cover full frame. Coma is pretty good, but f/4 is what we're talking about.