Can Protonmail import dsa1024 keys?

I have a public key sent by a friend. It’s dsa1024. I have imported this key into gpg and can encrypt messages with it. But, when I try to upload it to Protonmail for his contact, I get a message that it’s not a valid PGP key.

I can successfully upload other keys for other contacts. Here’s the result of gpg -k (with fingerprint and email obscured).

pub   dsa1024 2003-12-09 [SCA] [expires: 2021-06-06]       5----------------------------------------4 uid           [ unknown] ---------- <---@---.net> uid           [ unknown] ---------- <------@-------.com> sub   elg4096 2003-12-09 [E] [expires: 2021-06-06] 

Does Protonmail not support DSA 1024? Could I be doing something else wrong?