The Elementary OS greeter has support for fprintd via PAM.
First, install the required packages:
sudo apt install libpam-fprintd
Next, start fprintd if it's not yet started:
sudo systemctl start fprintd
Then, enroll a fingerprint:
Finally, enable the fprintd PAM module:
sudo pam-auth-update --enable fprintd
A fingerprint icon will now show ...
I believe this is the same issue I had, but you don't use disk encryption so you just see a black screen shortly on boot and then are greeted by the login manager.
See here for my solution: Black screen instead of plymouth
(Sorry, I can't post this as a comment because I don't have enough reputation)
I am on Hera - Elementary 5.1.
Tried many ways. This is the only way working for me.
None of the above solutions work at the moment. Following method works fine (tested in elementary OS 6 ODIN and OS 5).
Full guide: https://www.debugpoint.com/2021/07/change-lock-login-screen-background-elementary-os/
Open a terminal in your elementary OS.
Install git and following dependencies for greeter package.
sudo apt install git
sudo apt install -y ...