Some packages were collected from a very painful night of research and gathering, with a good amount of filtering out for bad / incompatible modules.

I don't even remember how I managed to find an obscure reddit post ( I think) with the other ones.

I packaged the .deb manually ( If i recall correctly ) and mashed up a bunch of methods until things finally worked in a stable way.

Unfortunately nobody ever replied me about the sources (no support whatsoever tbh). I own a Lenovo IdeaPad3 Slim which has one of the goodix fingerprint sensors and that's why I began this quest indeed

Thanks for the effort.

No, this needs libfprint-tod[0], which is built do dlopen non-free reader libraries from manufacturers.

[0]:https://gitlab.freedesktop.org/3v1n0/libfprint/

How does copyleft license work in this case? Aren't they legally required to open-source their sources and publish it publicly or can they hide that behind a request system?

IMHO a request system is sufficient. Remember GPL comes from a time where Internet was not granted and magazines with floppy disks were a thing.

Unlike the full GPL, the LGPL doesn't require applications of the library be licensed under the same. It would apply only to improvements to the library itself.

If you ship the library, the requirements for the library itself are very similar to the GPL.

The difference you describe mostly applies to system libraries (those libraries that are not distributed alongside applications).

No, the main requirement is that they link to libfprint dynamically or provide object files such that effectively you can replace libfprint with a different version of libfprint of your choosing, but there's no requirement to open source the work that makes use of libfprint.

Goodix fingerprint is used in Framework Laptop. This might come from that corner.

The fingerprint sensors in the Framework laptops already have open source drivers. This is for the sensors used in some older but still recent laptops from other manufacturers. I have a Dell XPS 13 from 2018 with an unsupported Goodix fingerprint sensor; I expect this would work with that.

Yes exactly it’s also the driver for my 2018 Dell XPS 15 and I think it was the last one missing for full linux support.

Actually, I have a Lenovo IdeaPad3 Slim and I had no idea of the Framework thing. Might be worth looking deeper for more devices support!