@schizanon Not sure why you think that @Vivaldi's "PWA support is non-existent", but it does have it.
To install a PWA through Vivaldi, you have to right-click on the tab (while that tab is active). There, you may get two options: "Install <PWA name>..." and "Create Shortcut..."
You use the former for websites that actually support running as PWAs, and the latter for every other website.
@schizanon@Vivaldi Ah, apologies, I hadn’t realised you were using the Android version. I’m on the desktop version (specifically macOS), so what I posted will be of no use to you on Android.
I’m not very familiar with the Android version, but from the information I could find in the Vivaldi forums, you apparently add them from the Vivaldi menu button (next to the address bar) and then select either “Install app” or “Add to home screen” - which one appears seems to depend on the website.
EDIT: Also, for some reason I can’t see the post you sent me before anymore… nor any of your posts 🤔