Uhm your question is a little un-organized + I have little mobile experiance.
Are you HUD widgets set to anchor in the center of the screen with the upper pivot point (not the transform one) changed to 0.5,0.5 from 0.0,0.0 and then location x,y set to 0,0 and size set to whatever the size would be?
You can then test your widgets in a variety of resolutions including a bunch of stock anodroid and iphones as well as computer resolutions by clickign the arrow in the top right hand corner of the widget designer you can also choose “custom” to enter in your devices resolution in both portroit LxW and landscape WxH mode to see if they work properly.
With everything setup to anchors when it asks you in the details panel properly it should scale to any screen perfectly.
One way to get the aspect ratio directly is to create a hud class (content browser → right click → blueprint class → all classes → search HUD) and then on DrawHUD event (search for it in the content menu) it will give you and X and Y float output pin for your viewports resolution every single frame. You could take those and divide them and then set that to a currentAR float variable and do math based on that.
Shouldnt be needed though. Anchors will take care of that. If the center anchor doesnt work on your device, try anchoring it to hte corners of the screen.
Let me know if this fixed your issue!
Don’t forget to accept an answer that best clears your question up or answers it so when the community finds your question in the future via search/google they know exactly what you did to fix it/get it going.