/usr/share/thumbnailers/librsvg.thumbnailer is in librsvg2-common 2.40.20-2.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 | [Thumbnailer Entry]
TryExec=/usr/bin/gdk-pixbuf-thumbnailer
Exec=/usr/bin/gdk-pixbuf-thumbnailer -s %s %u %o
MimeType=image/svg+xml;image/svg+xml-compressed;
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