Hi,
I am facing the same issue on a SLG2, although my fingerprint isn’t supported by libfprint, someone recently forked it in order to add support for the whole Surface Laptop Go line, and I’ve successfully repackaged that custom version of libfprint to make it work on my machine.
I was wondering if it was an issue on my side (I’m new to packaging on Nixos), and I just stumbled upon your post here. I’ll keep you updated if I find any solution.
edit : according to this : Fingerprint Reader with Gnome - #8 by jbhardman we should be able to get it working by supplying a driver to TOD.
Something that is also mentioned in the Nixos Wiki.
Unfortunately, in my case it seems like I can’t directly try this with the libfprint fork I used, probably because of me having to disable some tests in the libfprint package in order to make it build successfully. I don’t know if I should repackage libfprint-2-tod1-elan while disabling these tests as well.
However, following the instructions may work for you.