There are quite a few reasons for ledger/trezor not to support every forked shitcoin, but thats a different story.
With ledger/trezor you will always be able to claim your coins by importing the BIP39 mnemonic seed (12/24 word phrase) into another compatible wallet,
and use the generated private keys to 'claim' your forked coins in their appropriate wallet.
But this should be done carefully. After typing your seed into your pc you should regard your wallet as compromised.
So to be on the safe side, first send your BTC to a new wallet, then import your old priv keys to the fork-coin-wallet software.
Important note that if a coin doesn't plan on supporting replay protection (like Segwit2x was about to) then sending your BTC out of your wallet first without splitting it would result in the loss of your other coins at worst, and at best you just moved both coins to a different address.