I've found doing face pulls at the gym significantly helped build up all the supporting back/neck musculature that I was beating up sitting at a desk all day. Rows also were pretty helpful for my lower back.
It'd be sort of difficult to do without equipment since it's a cable exercise. If you didn't mind buying some resistance bands, and have a reasonably stable point somewhere at head-height to loop them through as an anchor, you could do that at home. (It's an exercise that you're supposed to do with reasonably light weight, so it wouldn't need to be too sturdy.)
EDIT TO ADD: this article has some explicit advice on how to adjust it to do at home on resistance bands: https://athleanx.com/articles/shoulders-for-men/stop-doing-f...
It's actually better to start without equipment because those muscles are typically very weak for people who haven't specifically exercised those muscles
Though there are other ways to work the rear delt. I prefer some rings at home.
I had shoulder surgery after blowing out my AC joint weightlifting. I went to one PT place that, while good in some areas, focused on strength of my rotators and neglected my mobility. My shoulders got worse after initially getting better and I thought I would need a second surgery. Fortunately I screwed up my lower back so I sought out a new PT place(Catherine at Fields in Motion, Campbell, CA) which not only fixed my back, but identified what was wrong with my shoulder and helped me fix it. It's only now, after months of flexibility and lower-trap strengthening that I know what a face pull is supposed to feel like.
Keep those sternums out, shoulders rolled back, and always keep your core activated(squeeze your cheeks and tighten abs) when you do anything physical. It seems so obvious now, but I went 45 years without figuring it out.