How to record line level input on an Android phone

This allows an Android phone to record the audio-out from another device. In this case, it's done in a way that's undetectable by other people.

Line-level attenuator

This converts line-level input into mic-level input.

• https://www.amazon.com/gp/product/B0F9DR496H

Microphone 3.5mm ⇒ USB C adapter

• https://www.amazon.com/SABRENT-Microphone-Compatible-Smartphone-AU-PACM/dp/B0F7QPSJH3
• https://www.amazon.com/gp/product/B08V5MH1MT

Most phone apps can only record from mic-in but not line-in

How to configure specific apps to record from line-in (this only applies to audio input adapters that provide both mic-in and line-in, or that only provide line-in which is probably rare):

• https://www.reddit.com/r/pocketoperators/comments/1ife7hm/linein_recording_on_android_details_in_comment/