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Yes, I use it a lot. Gives me the freedom to carry my encryption keys (GPG) with me securely and I am able to use it on several systems.

Can you specify a few good use cases?

logging in to github, google, your own PC, ... key to keepassxc saves multiple (x509) certificates

Great. Do Macs let you login with these? Let me google that.

I use it to store my GPG key and as a U2F key for my Google account.