I don’t know about a metal cord protector but here’s a different solution just in case it doesn’t exist. when my cat wouldn’t stop chewing on cables, I got bitter apple spray, collected all the cables in my house, put them all in my bathtub and sprayed them all very liberally with this bitter apple spray, let them dry then plugged everything back in. Now the only time I have a cable get chewed through is when I just got something and I forget to spray it cuz I guess she still tests them just to be sure they taste awful. And believe me, it tastes awful. I highly recommend wearing disposable gloves while handling the stuff, especially while it’s wet and then washing the bathtub and your hands thoroughly once the cables are dry and back where they go. Blegh!
I use fastmail for the email alias ability. Proton doesn’t have as robust a system for creating lots of different email addresses that all go to the same place. Also proton is only encrypted if both parties use proton so it’s security claims are diminished in my eyes. It’s better to assume nothing is encrypted than to think everything is and be wrong.