Thanks for the tip, definitely helps a bit. Sadly, it stills crops a small part of stories for me, but I guess it will have to do since Samsung/Instagram seem to have no interest in fixing the probelm
The entire Facebook family (Instagram, Facebook, WhatsApp) have always been focused into the Apple's ecosystem. It's incredibly optimised to work fantastic onto that environment. It has always been like that. Always! Whether you have a Samsung or Huawei, LG or Sony, if it's an Android system, you'll be facing a ported version. Please stop blaming Samsung for that, it's not its fault. Complain on Instagram and they won't even care. Get an iPhone and be amazed.
Update! I was browsing stories on my Galaxy S10+ today and realised the stories now have black borders to fit the entire image on the screen! Seems the issue was fixed in a recent update. Finally.
Just got A50 last week. Same problem. Try the app Unfold. You can adjust how you want your image to be seen. Try each frame then post your story and see how you like it. I find it best to have two phones by side for comparison. It is very confusing at first, takes a bit of time and effort too but you'll get the hang of it.