Regarding the coins i found no way to add Algorand and Polkadot in Trezor, and Ledger natively supports them without installing 3-rd party apps.
Trezor doesn't support either of the two altcoins that you mentioned. You can always check
https://trezor.io/coins for information on supported coins and tokens. The only asset Trezor supports is something called 'Binance-Peg Polkadot.' It seems that it's a BNB Smart Chain token that is pegged to the value of Polkadot. You will need a 3rd-party software wallet to manage that asset. Trezor's website mentions Rabby and Metamask.