That being said, I don't know if the Electrum server ignores policy rules, or if your Electrum client will allow you to do that.
I tried it in testnet Electrum that is connected to their server:
electrum.blockstream.info:60002;
And it does accept replacement transactions even without the opt-in RBF flag.
Considering Electrum mainet and testnet works similarly, it may actually work depending on blockstream server's node in mainnet.
Creating the replacement transaction for full-rbf cannot be done in Electrum GUI though.
Here's the test transaction:
https://mempool.space/testnet/tx/85161f67da19ab4715e6ade401ecedb5fdda2eceb84ac4b9d2663e6952ca6aa8Didn't opted-in for RBF but tagged in mempool space as "
full-RBF".