Couldn't find a single one. Only TCP or TLS. Am I looking in the wrong place? ( https://1209k.com/bitcoin-eye/ele.php?chain=btc )
They are rare because Electrum and all the other wallets using the protocol do not support it client-side, so nobody setting up an ElectrumX server has any incentive to enable this. ElectrumX requires you to enable individual protocols explicitly. Furthermore, as you can see in the changelog they have only been supported since May 2019.