# if you are on MacOS start with brew install ykman
# if you are on archlinux, install extra/yubikey-manager so you have ykman

# Now insert your first yubikey

# -t is for touch. If you leave don't add the -t switch you never need to touch your yubikey for auth.
sudo ykman otp chalresp -t 2
WARNING: PC/SC not available. Smart card (CCID) protocols will not function.
ERROR: Unable to list devices for connection
Enter a secret key: 8173cbe36a468545ac0df5f448c4d7e120feac3d (random key generated from YubiKey Personalization Tool)
Program a challenge-response credential in slot 2? [y/N]: y
challenge-response credential stored in slot 2.

Unplug Yubikey
Repeat for each Yubikey.

Backup your KeePassXC Database.
Now go into your KeePassXC Database => Database Security
Then click on Add Challenge Response and then Change Password and enter your current password there and confirm it.
Press Apply.

Now test with all your yubikeys if authentication does work as needed.