AFAIK, the two most common sets of HD wallet mnemonic seeds used are BIP 39 compliant or Electrum Wallet compliant. Most of the more secure hardware HD wallet devices support the BIP 39 standard, which appears to be deprecating the older set of Electrum HD seed words. People should not have to do a deep dive into Electrum Python code to find the list of wallet mnemonic seeds. The old Armory paper mnemonics backups are too difficult for non-technologists to utilize, and should be treated as deprecated.
With the BIP 44 standard being defined across a plethora of altcoins, and HD hardware wallet vendors supporting BIP 39, I'm thinking the prevalence or days of using Electrum mnemonic seeds will be numbered.