Outlook PWA unavailable

A few weeks ago I discovered a bug in the Outlook Web App. The icon to install Outlook as PWA in the address bar (see below) is not available, if the language of the OWA is any other language than English. The bug exists for several months.

This is the missing icon:

I did some further analysis on the bug and found out, that the root cause are wrong manifests delivered through https://outlook.office.com/mail/manifests/pwa.json?culture=en (the culture varies depending on the selected language).

For English, the manifest looks like this, which is correct:

{

        },

{

    ],

I opened a ticket with Microsoft, which was tracked under 2307211420000339. However, The ticket got closed two times. Microsoft keeps telling me, that the problem is caused by my browser, although the problem is reproducable with different browsers on different systems.

So here is the question: What should I do to make Microsoft fix the problem?