I know this question has been asked numerous times in the past (when the answer was still “There are plans to do so”).
Last week I spoke with Microsoft tech support who said it was possible and all I needed to do was sign up for a trial subscription to Portals (I currently have PA Plan 1). I have since signed up but don’t see any way to share an actual app.
It has been a bit confusing in speaking directly with Microsoft support. I was under the impression that canvas/model PowerApps sharing was part of the PowerApps Portal sharing platform. This is also what Microsoft Tech Support led me to believe.
I now understand it is it's own program and though you can now share with external users, your must assign them a license to do so. I was hoping it would have been like Portals where the user could sign up with their own credentails without the need to have a microsft, etc. account.