> Have you tested that it works?

Yes. I wouldn't have mentioned it if it didn't work.

Here's a screenshot showing the Apple and PayPal 2FA codes I have received through Slack via Twilio...

https://i.imgur.com/bQYSbPZ.png

I also don't have any accounts with banks that are stupid enough to use SMS for 2FA [1] so I haven't needed to use my Twilio number for that purpose.

Using SMS for Gmail 2FA doesn't make any sense when Google supports U2F.

[1] https://motherboard.vice.com/en_us/article/mbzvxv/criminals-...