Most MFA implementations will balk as soon as they discover you're on VoIP.
And they will.
And they will.
I signed up for my number in 2015, with a landline, because I had just purchased an Android tablet, with no SIM slot or mobile plan, so I decided that teh Goog was the best bet for VoIP for me.
You've got to guard your conversations on Voice, and don't mention forbidden keywords. Voice will instantly disconnect the call if it detects wrongthink.
I don't see how Google makes money on Google Voice, which makes wary of them shutting it down some day.