ykls is a utility for listing connected Yubikeys, along with some relevant
information, such as enabled modes, firmware version, serial number,
identities present in the various key slots, ...
.
For example:
$ ykls
Reader: Yubico YubiKey FIDO+CCID 00 00
Version: 4.3.7
Serial: 6447364
Slot Authentication (9a): nicoo@debian.org
Installed Size: 2.1 MB
Architectures: amd64 arm64