I’m not saying that this is the answer or preferred method… but one can record an action to insert the zoom level of choice into an action. Then this action can be automatically played on each opened image via the Script Events Manager.
Hopefully Staff or another volunteer will see this and may have ideas. For the time being, use Ctrl+1 or Ctrl+0. Let us know if any of these other threads help you.
I have looked at the same old threads. Unfortunately following the suggestions from them haven't resloved the issue for me; that's what led me to look for an up-to-date answer on here.
To add to my query. I basically just want photoshop to show an image at it’s actual size when I open it. Does anybody know the setting for this? I just thought it did this automatically like it has done for me for the last 20+ years.
That's just the zoom level — nothing is broken. New documents can open at 100% in a large window, which makes a smaller canvas look tiny, like in your screenshot.
Press Ctrl+0 (Windows) or Cmd+0 (Mac) — that's View > Fit on Screen — to fill the window with your canvas. Press Ctrl+1 / Cmd+1 for 100% (actual pixels).
More on zooming here: https://helpx.adobe.com/photoshop/using/viewing-images.html