enable PGP Public Key Export in V3
Enable OpenPGP Public Key export from Settings -> Security from V2 interface in new V3 interface
We are working on full key management for v3.
It would be nice to have an exposed public keyserver, so that someone outside of protonmail can search there for my public key (using GnuPG or related products) and find it.
It's 2019 now...
I don't know why it has been disappeared...
Protonmail needs to look into getting inter-operable with PGP.
Otherwise, there are couple of decent solutions out there (mailfence, scryptmail...)