I personally recommend EdDSA - just one letter difference, but a very big one under the hood! (If you're using `-t ed25519` then you're using EdDSA.)

EDIT: Github agrees with me: https://docs.github.com/en/authentication/connecting-to-gith... they recommend EdDSA/ed25519 as first option, and RSA as fallback. ECDSA is not in the list at all.

EDIT2: gitlab (https://docs.gitlab.com/ee/user/ssh.html) also recommends ed25519 (which uses EdDSA for signatures). They'll grudgingly let you use ECDSA but point you to https://leanpub.com/gocrypto/read#leanpub-auto-ecdsa for a lecture on why it's a bad choice; there are actually more problems with it than the ones covered on that page that would be far harder to fix.