There are free, open-source, and privacy-respecting options for TOTP 2FA that don't require a mobile phone plan.
You can use something like KeepassXC (desktop) or something like KeepassDX or Aegis (on F-Droid on Android) for your OTP authentication app to manage 2FA for Google, Amazon, eBay, Dropbox, etc. and there are other options as well.