Voice input device list fails to show all available devices, refuses to scroll, and cannot be resized.

[foresto]

Your system information

• Steam client version: Sep 20 2019, at 00:06:06
• Ubuntu 18.04.3 LTS
• Opted into Steam client beta?: Yes*
• Have you checked for system updates?: Yes

*Although I am currently opted in to the client beta, this bug was present before I opted in. It has been present for months, ever since the big steam client update that redesigned the friends list / text chat window and moved voice settings out of the main steam settings panel.

Please describe your issue in as much detail as possible:

I want to select my microphone for voice chat.

Steps for reproducing this issue:

1. Open the Voice Input Device drop-down list to find the right device.
2. Notice that the list is a fixed size with no way to scroll, and its parent window cannot be resized, leaving me with no way to see all my input devices, let alone select the right one.

[foresto]

To be clear, this prevents voice chat from working at all, because there is no way to select the microphone.