Note of service: I addressed the issue in gitlab of openmw and they are working on it; however, at the moment I'm keeping this article on. Maybe I'll hid it in the future when the problem is fully solved.

Update:
Openmw team solved the problem and released a new dev build.
They were also so kind to update me on this: assistance 10/10.
The tweaks below should not be required anymore, but for now I'm leaving this page on, to be informative and to give my thanks to the team that solved the problem.
Have a good game to you all.


This is not really a mod but a little guide to get rid of shadows artifacts in openmw (if you like me experienced the same issues). In addition, in the download session you can download the settings I used to overcome this problem.
Why I put this article here? Because I found it difficult to understand and resolve the problem and I hope to help others with this.
So, let's get straight to the point:

recently I decided to use openmw 0.49 dev instead of 0.48 stable release, but as soon as I launched a game session I encountered some graphical issues; namely: some flickering shadows over the buildings, trees and other vertical meshes.
Initially I thought that this was a problem of how dev version handled normal\specular maps of some textures, but the more I examined the problem, the more I discovered that this wasn't true at all... or.. maybe partially true cause, previously to the change, I did not encounter such difficulty with the stable release at all.

after some headaches and some research, I found that this was a some sort of common problem with previous releases and with this article (https://forum.openmw.org/viewtopic.php?t=5857&start=20 ) I managed to overcome the problem with some tweaks on settings.
Why default settings of 0.48 do not suffice to 0.49 anymore I cannot tell..

But what I was experimenting? I delved into it and discovered that the issues that I was noticing are a variety of shadows artifacts that occurs in rendering and gaming, this article (https://learn.microsoft.com/en-us/windows/win32/dxtecharts/common-techniques-to-improve-shadow-depth-maps ) was a pleasant and unexpected surprise for me to deepen my knowledge.

So I discovered that other than flickering shadows I was watching at Shadow Acne artifact on some plane surfaces.

The resolution forum of openmw (a necromancy thread at this day) ends with a user thanking the others for his resolution of the problem with these settings:
[Shadows]
enable shadows = true
number of shadow maps = 4
allow shadow map overlap = true
split point uniform logarithmic ratio = 0.5
split point bias = 0.0
enable debug hud = false
enable debug overlay = false
compute tight scene bounds = true
shadow map resolution = 4096
minimum lispsm near far ratio = 0.25
polygon offset factor = 1.1
polygon offset units = 4.0
normal offset distance = 8.0
use front face culling = true
actor shadows = true
player shadows = false
terrain shadows = true
object shadows = true
enable indoor shadows = false


that surely resolved Shadow Acne with this option
use front face culling = true
but there is something wrong in it...
if you go to the openmw guide to settings ( https://openmw.readthedocs.io/en/stable/reference/modding/settings/shadows.html?highlight=shadows) you will notice that normal offset distance = 1.0

and not:
normal offset distance = 8.0
so what will this user create with this setting? A Peter Panning of vertical shadows! you can easily spot it on the stone windows of seyda neen
and what if instead I maximise offsect factor? for example polygon offset factor = 8.0

It will create another Peter Panning stretching the shadows: orizontally this time

so what did I do to stay in the middle and to get rid of the flickering that was still slightly present?
Testing..
and after some tedious tests I found for me a sweet spot:
polygon offset factor = 1.6
polygon offset units = 4.0
normal offset distance = 1.5

edit:
(slightly "abusing" offset factor does not generate big visual issues and better manages flickering without offset distance "vertical" peter panning - new file 1.1)
polygon offset factor = 2.1
polygon offset units = 4.0
normal offset distance = 1.0

What did I get? ridding of some noticeable flickering
What did I gave? some almost unnoticeable Peter Panning
Yes, the blanket is short! (meaning you can't fully cover your feet and your nose at the same time)

so If you are ok with my settings just download and copy\paste otherwise tweak it by yourself
I put some images to let you understand what I'm saying here.

note:
with the same- "testing philosophy" I also tweaked in Terrain "max composite geometry size = 1.0", cause I found that this improved rendering of textures instead of default 4.0 without any major fps drops.

The settings file is mainly for share of my experience and for future personal use, so feel free to grab it, tweak it or discard it completely.
Have a good game!