Steps

Purchase this yubico key (YubiKey 5 NFC): https://support.yubico.com/hc/en-us/articles/360013656980-YubiKey-5-NFC

Follow this article first: https://support.yubico.com/hc/en-us/articles/360016649039-Enabling-the-Yubico-PPA-on-Ubuntu

The OS I installed on was Ubuntu 21.04

# lsb_release -a
No LSB modules are available.
Distributor ID:	Ubuntu
Description:	Ubuntu 21.04
Release:	21.04
Codename:	hirsute

Next, this article: https://support.yubico.com/hc/en-us/articles/360016649099-Ubuntu-Linux-Login-Guide-U2F