I'm using Vivaldi on my Android smartphone (Pixel 9a) for a while as my default browser. Only recently I've started noticing that Vivaldi is having issues with (I guess it is called) "app-to-app communication".

Some websites offer you to authenticate with another app (where I live, itsme is extremely popular) and this concept doesn't work anymore on Vivalid. You basically click on "authenticate with itsme" and it should open the itsme app where you authenticate and afterwards you are forwarded back to the Vivaldi where you are then authenticated.

I quickly installed Firefox to check if the issue is somewhere else and Firefox does it just fine. Also the other authentication apps Belgian eID has simply the same issue only with Vivaldi.
A website where it should work is https://www.minfin.fgov.be/myminfin-login/pages/public/login (choose My eGOV or itsme). When I visit it with Vivaldi, choose one of the 2, I get the page that I need to install the app while it normally should open the app.

I also remove Vivaldi entirely and reinstall it, but that didn't help either.

I hope I've made the issue clear as for me this is blocking. I use such websites too often to not being able to use it anymore so I hope someone can help me. Is this a known issue or is it just me?

Thanks