What is your go-to way to catch mobile UI bugs on devices you don't own?

Just realized my mobile conversion issue had nothing to do with copywriting.

On slightly smaller phones, the main sign-up button was getting pushed down so far that people had to scroll just to see it.

Because it looked fine on my phone, I assumed everyone saw the same thing. I only spotted the issue when I happened to look at my site on someone else's screen.

Curious how others handle this do you use browser testing tools, or do analytics usually give away these layout problems first?