12-words mnemonic phrase for shelley era wallet

I noticed that some wallet applications are able to generate shelley era wallet from 12-words mnemonic phrase.
I’m talking about ledger, eternl and trust wallet (probably some others as well).
In both eternl and trust wallet if I recover a wallet from my 12-words phrase I got the same addresses generated, so it seems some standard of how it is done exists.
Ledger generates different address for me, so it is done in other way there.

  1. I wonder how does it work? Does this wallet apps add some specific words to my recovery phrase to make it up to 15 or 24?
  2. Is there a way to recover a shelley era wallet from such mnemonic phrase in Daedalus?