In Windows mixer I can control the Line-in volume, but in EarTrumpet it doesn't exist. See screenshot below

Interesting issue, thanks. Will take a look at this.
I don't know if this universally efects everyone, but I also have no line in control
I think this started working in one of the early 2.x builds, and with 39438eac212f4d55693b85336c5be7de935eb199 the icon and text will be correct.
Closing. Please re-open this if you run into issues.
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Interesting issue, thanks. Will take a look at this.