Trying to import a wallet phrase created using Electrum into Proton Wallet currently yields the following error:

Wallet seed phrase checksum is invalid. We only accept BIP39 seed phrases and do not support Electrum ones.

It would be nice if importing Electrum / BIP32 wallet phrases was supported.

Many people used Electron back in the day because it was the best open-source wallet available at the time. People might want to avoid creating a new wallet with a new address (the old one might already be known) and/or transferring their Bitcoin (due to fees).