Detection of login fields not working on greenpeace-energy.de

[chrthi]

On https://mein.greenpeace-energy.de/ keepassxc-browser fails to detect the login and password fields. Even when trying "Choose custom login fields", the fields aren't offered for selection.

Expected Behavior

The KeePassXC icon appears in the "E-Mail" field.
Username and password are filled in when clicked.

Current Behavior

The KeePassXC icon is not shown in any field.
Choosing "Fill Username and Password" from the context menu of either field does nothing.
Clicking the KeePassXC-Browser button in the browser's menu bar and choosing "Choose custom login fields" greys out the entire page; no fields are offered for selection.
On other pages KeePassXC works normally.

Possible Solution

I suspect that the algorithm for detecting login fields doesn't work with this specific kind of SPA and could be extended.

Steps to Reproduce (for bugs)

1. Prepare a KeePassXC with an opened database and working KeePassXC-Browser integration
2. Add an entry (made up, if needed) for https://mein.greenpeace-energy.de/
3. Visit the page

Debug info

No messages in the the browser's JavaScript console.
KeePassXC - 2.6.2
KeePassXC-Browser - 1.7.4
Operating system: Linux x86_64
Browser: Chrome/Chromium 90.0.4430.93

[varjolintu]

Those login fields are inside a Shadow Root DOM which we support only partially.

[varjolintu]

Now tracked in #1358.