The Model T’s firmware supports ADA, meaning it can perform operations for that coin on your device. Your private key never leaves the Trezor when using these third party wallets. In short, you are still using a hardware wallet (your Trezor) with these third party wallets (such as AdaLite or Yoroi). As long as you follow the security best practices and navigate carefully, your funds are safe.
And also, Cardano support in Trezor Suite is on the roadmap (see here). No third party wallets needed soon 