Recommended strengthening/stretching exercises to improve shoulder mobility

An SS video [1] discusses a suggested strech to improve shoulder flexibility to enable the recommended [2-8] grip.
That is, (if I understand correctly)
(a) all fingers at least touching the bar,
(b) straight/neutral wrists, and
(c) hands as close together as possible.

When ensuring (a) and (b), my hands are rather far outside and I get elbow pain.
When ensuring (a) and (c), my wrists seem to be in danger: in particular when using (more) heavy weights at some point in the future.
For now it seems to be acceptable when using wrist straps for support but that seems to be tackling only a symptome of shoulder immmobility.

The video [9] also discusses an aparantly confusing question for another athlete where Rip states that, with the limited information available on the athlete, pain should be avoided.
Also, I am aware that the symptoms are recurring [11] a lot on the SS forum though.

Are there other recommended strengthening/stretching exercises to improve shoulder mobility to enable (a), (b), and (c) from above?
There are many videos on stretching the shoulders but [1] seems to be the only one with the purpose of achieving the desired grip for low bar squats.
While using some/all of the exercises available on youtube may be effective, this is certainly no optimal approach with respect to time efficiency.

Why is the bar placement in the low bar squat healthy when the (to me) similar position is reached in the bottom position of the unfavourable [10] 'behind the neck press' exercise?
Does that reasoning also exclude behind the neck pulldowns even with light weight from being a suitable strengthening/stretching exercise?

My stats for the case it is relevant to the matter:
age = 36
height = 6.3" / 193 cm
weight = 95 kg
squat = 95 kg
press = 55 kg
deadlift = 115 kg

[1] Paul Horn; Low Bar Position Stretch | On the Platform; 2016; YouTube
[2] Mark Rippetoe; The Squat - Bar Position with Mark Rippetoe; 2012; YouTube
[3] Mark Rippetoe; Proper grip in The Squat | Starting Strength; 2015; YouTube
[4] Mark Rippetoe; Squat Grip Correction | On the Platform; 2016; YouTube
[5] Mark Rippetoe; A Clarification on the Squat Grip | On the Platform; 2017; YouTube
[6] Mark Rippetoe; Fixing the Squat Grip - Starting Strength Seminar; 2018; https://www.youtube.com/watch?v=w0hx5Dtctjw
[7] Mark Rippetoe; Learning to Squat | The Starting Strength Method; 2018; https://www.youtube.com/watch?v=nhoikoUEI8U
[8] Mark Rippetoe; SQUAT Pro-Tips w/ Mark Rippetoe | Starting Strength; 2019; https://www.youtube.com/watch?v=iVx2O6PXb6U
[9] Mark Rippetoe; Shoulder Flexibility In The Squat | Starting Strength Radio Clips; 2019; https://www.youtube.com/watch?v=TRMtK-FIIFE
[10] SS Forum Members; Thread: Behind the neck shoulder press; 2015; https://startingstrength.com/resourc...der-press.html
[11] SS Forum Members; Thread: Squat wrist pain; 2019; https://startingstrength.com/resourc...rist-pain.html

I don't think I've ever seen a post with citations, so that's neat.

Maybe post a video of yourself where we can see the grip/bar placement clearly and understand what you're working with. It may not be a flexibility thing at all.
There will be times, though infrequently, where we have to adjust the grip outside of what is exactly in the book. Darin Deaton wrote an article on the "thumbs-around" grip for example.

I will post a video once my gym buddy is back from vacation.
I read the article Thumbs-Around Grip | Darin Deaton you mentioned and for the time being I am actually using the "thumbs-around" grip already, which allows me to move the hands close to the shoulders where the forearm is even perpendicular to the bar.

I have not managed to shoot a good video.
The best I could come up with is this one: YouTube

A couple of weeks ago, I had the impression that I had problems because I was pushing the bar from below with my arms when using a narrow grip (basically having a vertical forearm).
In a high-bar squat I did this before to stabilize the bar on my back and also to tighten the back.

I then changed again to the recommended grip (hands above the bar, neutral wrist) but I am using a very wide grip.

On warmup sets I feel the bar resting completely on my back.
But when the weight gets heavy, I suspect that I am pushing the bar into my back more.
I guess that I am distracted in such heavy sets...
In the video I got the the (left) elbow pain again.
The only thing I notice is that the angle of the upper arm does not follow the angle of the back, which I understand that it should.

Do you have further insights based on the video?