How many bitcoin Electrum wallets does Lrdger Nano S support simultaneously?
It depends what is your interpretation of "wallets". By design, there is only one seed per Ledger. But, the same Ledger seed may create multiple "accounts" and you can keep track of each one of them using Electrum. Each account will have its own Electrum wallet file and name (most recent Electrum version) - but they all share the same seed.
Like Trezor, the same Ledger seed can also create simultaneous alt-coin wallets in the device, for supported coins, like Litecoin & Dash, and can be accessed using Electrum clones, like Electrum-LTC or Electrum-DASH - or Encompass, which is a multi-currencies Electrum clone.
As you can see, one seed, multiple accounts, multiple coins, all in one hardware device - thanks to BIP32 and 44.
The draw back - you loose your seed (or it gets stolen) - you may loose all your coins and all your accounts at the same time (if the thief is aware that you have "extended" your seed in such a way - of course).
Where that differs with the Trezor, in my applications anyway, is that the Trezor wallet utilizes passphrases for each of my wallets. This would make SEED compromise only one piece of the puzzle for the thief. Unless the thief also had each password he/she would not be able to access any coins "related" to that SEED and password combination. The downside to using my Trezor in this matter is that I too MUST have all passwords or I lose my coins.
