Neither using the QR code option or the email option work. Both result in a white screen. By using the iPhone's camera to scan the QR code (instead of using Firefox) I can see that the QR code is point to https://mzl.la/MYCODE. This URL in turn is redirecting to https://app.adjust.com/somecode?campaign=firefox-desktop&adgroup=firefoxview&creative=CODE-123. Opening this URL in Safari gives me a white page with a "Download App" button to download Firefox (which I already have installed). My Firefox account has the setting "Allow ⁨Firefox Accounts⁩ to send technical and interaction data to ⁨Mozilla⁩." set to off. So probably none of this tracking should occur. In any case, I went to Firefox settings and turned on "Allow Cross-Website Tracking". I also went to Safari settings and turned off "Prevent Cross-Site Tracking", "Privacy Preserving Ad Measurement" and turned "Content Blockers". Then I tried syncing again. The result was the same white page as before.