This file is indexed.

/usr/share/alsa/alsa.conf.d/README is in libasound2-data 1.0.27.2-3ubuntu7.

This file is owned by root:root, with mode 0o644.

The actual contents of the file can be viewed below.

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You can place files named *.conf in this folder and they will be processed
when initialising alsa-lib.