I’ve found a way around it as saving it to files isn’t a suitable option when you need to access it without a white background for use in other apps. I’ve done a screenshot tutorial to the best of my ability. First you want to download two apps if you don’t already have them. An app called “background eraser” and one called “Picsart” they look like this:

when you import your png into background eraser, the white background iOS 13 is adding is no longer there. So then, you want to click this: 
if you haven’t paid to remove ads, you have to watch a video ad for 5-10 seconds. Make sure the 5-10 second timer is up then X out of the ad.
then, click this:

it will give you PicsArt as an option if you have download picsart and created an account. It should also let you choose to import into any of your photo editing apps.

click import

Click next

Click post (you can delete later, after you have done what you gotta do)

Click done

then, to access your png, go to your profile. Click the little person looking button to the far right. 
your png will show up under stickers. I believe you can also export from picsart to most of your editing apps. I hope this helps. 😘