LENOVO Thinkpad Carbon X1 Gen8: how to use the 3.5 mm TRRS jack as stereo line in?

Situation I've got a Lenovo Thinkpad Carbon X1 Gen8 (Model 2OU9 - 0006GE ) here, which features a 3.5 mm TRRS headphone/mic combo jack. I'd like to plug a 3.5 mm TRS stereo line in cable from my analog mixer into this jack, in order to record the audio signal with the laptop. However, the Thinkpad insists on recognizing any TRS cables as a pair of headphones and won't allow me to change this from output to input anywhere. On the Dell laptops I've used so far, there was this Which device did you plug in? prompt shown below, which gives me the option to select line in instead of headphone and re

Question by M463 on Super User, licensed CC BY-SA. We show a short excerpt and link to the original thread as credit.