Desktop screen in portrait mode breaks the layout of chats

[Giszmo]

Describe the bug

Narrow screens make the chat increasingly unusable to the point where the text input disappears behind the tab icons.

Scrolling to the right to find the send-message button makes the top-left icons partially disappear behind chats.

Steps to reproduce

Open a message under messages on a narrow screen or increase the font size.

Environment

Debian FF

For me the issue appears on a portrait-mode screen with 1:1 scale.