Scapular mobility

Hi all-does anyone have any experience with scapular mobility issues?

I’ve watched numerous SS videos on stretching to get under the bar (and loads of other resources too) but still have major mobility issues/pain in my right shoulder.
Basically I feel it is scapular mobility holding me back (bench is pathetic too as I struggle to retract scapula and lie flat on the thing-oddly enough OHP is pretty strong and when I was training regularly it was actually stronger then my bench...)
—had loads of physio (£70 an hour) which amounted to no improvement at all-this lady has worked with Olympians and had no idea where my issue came from
—chiropractor, another waste of money
—cortisone injection in rotator cuff-did nothing
—ultrasound and scans at hospital did diagnose me with ulnar nerve issues/cubital tunnel syndrome (pencilled in for surgery but that got binned due to Covid...not sure I really want it anyway now)
Basically I feel like I can live with the pain which is mainly front delt and inner elbow but can this be connected to the shoulder mobility as well?

Tried an absolute ton of mobility stuff, band work, stretches, postural things but I have no chance at all of getting my right side into the low bar position without adopting some weird talon like grip with the right hand and even then the bar doesn’t quite feel even or “locked in place”.

Drives me mad to see people just perfectly retract their scapula and get right under the bar.

The only thing that gets close is a doorway stretch alternating the position of my hands (I.e higher and lower up and down the doorframe). At times it feels like my scapula is almost getting “unglued” and is going to slide back into position which is briefly oddly exhilarating but it never quite gets there...even then at the gym I spend more time stretching than under the bar.

Posture isn’t great (desk bound job and also play guitar quite a lot) it almost feels like my body has totally trained itself to sit in the wrong position but then I think if the issues were entirely postural surely one of the ‘specialists’ I’ve seen would have diagnosed? Instead they’re all scratching their heads.

Sorry for the long post but can anyone sympathise or shed any light?

Try pushups with full protraction at the top, chin-ups with full protraction (dead hang).

The best stretch is getting under a loaded bar and lift just enough to push the bar where it needs to go. If it doesn't quite make it, hold it for a while, 30-60 seconds. Relax. Try again. Do it again tomorrow, etc.