Firefox relies on gtk for for those integrated buttons. It’s maybe worth checking that your gtk theme is set to breeze in System Settings > Colours and themes > Application style > GNOME/GTK Application Style (top right …), and that firefox is set to use the system theme.
When you install whatsapp, if you deny it permission to access your phone number, or if it doesn’t find one, it allows you to enter a phone number manually. It then sends a confirmation text with a code to verify the number, just like any other website.
I used an old (non-smart) phone with a burner sim to receive the confirmation text.
I don’t use it for every day apps, but for accessing things that are only available as an app:
I know a couple who got married in a 2-person camel costume.
Exactly. I created my whatsapp account in waydroid like this.
It can be pretty complicated without a phone. Especially if your computer doesn’t have a webcam.
You can export from draw.io with dark mode and grid enabled as well. Seeing as the space even on all sides…