Solved Passwordless Microsoft Account

What would happen if I have both Two Step Verification and Passwordless Account turned on in the Microsoft Account and I lose access to the Microsoft Authenticator app such as app deletion, factory reset, or lost device? Do I need to have at least two or three pieces of security info before turning on both Two Step Verification and Passwordless Account? I also have a 5x5 Recovery Code printed and kept in a safe location as well. Will a Yubikey work as a backup in case I lose access to the Authenticator app?

The authenticator app should have the option to backup the contents - the iOS version does - so after uninstalling the app or installing on a new device I would choose recovery, sign in to my Microsoft account & it recovers the entries.
When you turn on 2FA the app/site will recommend you backup the recovery codes so you can log in if the authenticator app doesn’t work for some reason. I would certainly do this.
I can’t comment on Yubikey as I’ve never used that.

You can enter your cellphone number and have sms as a backup. You can also provide a second e-mail address as alternative verification step.

2FA is already double-edged sword, going passwordless is just the latest MS toy that will go terribly wrong.

Make sure to backup your recovery code!

I don't have a cell phone, only an alternate iCloud email address on my iPad.

Use a single very tough password, if you have no other means to verify your account.
Even though a password can be hacked, I would not go passwordless on my MA.

My limited experience with MS Authenticator led me to believe it's not ready for widespread use, yet.