Export your OTP database to an (optionally) encrypted file on a USB stick and put that in a lockbox/somewhere safe. If encrypting the stick/file: make sure you use a memorized/written down password.

You can set up a VPS and tunnel that to your minecraft server using wireguard some iptables magic if you’re into Linux.

It has had quite a bit of downtime/undercapacity issues but for me it’s has been working fine the last year at least.

I think some work was being done on rewriting the backend to make it more efficient but I don’t know the exact state of that currently.