Firefox iPadOS User Agent Problem

Have been using Firefox on iPad for a year now.
Did not know since when, websites have begun to discriminate Firefox iOS.

For a while ago, I usually uses WhatsApp for web in desktop mode, it could perfectly send and receive new messages.  But now, it won't work, the website just keep saying my browser is out-dated, please update to other browser.

I do not know what is this happening, until I found the user agent seems to be changed.

So from now on, the desktop mode is basically broken.  Major sites like Google, Zhihu, Quora just won't work fine with it, forcing me to use the mobile version.

fixed now: https://bugzilla.mozilla.org/show_bug.cgi?id=1587388