Is it possible to convert BTC to other alt coins inside trust wallet directly ?
Simple googling would give you the answer;
Trust Wallet supports two types of swaps: "interchain swaps" that allow you to exchange coins/tokens within the same blockchain, and "cross-chain swaps" that facilitate the exchange of coins/tokens across different blockchains. Regardless of the type of swap you opt for, Trust Wallet ensures a smooth and hassle-free process.
For instance, if you have Bitcoin (BTC) and wish to acquire Ethereum (ETH), Trust Wallet allows you to make this conversion directly within the app, eliminating the need for complex protocols, bridges, or third-party applications. But it doesn’t end there, you can swap any ERC20 token Trust Wallet supports and swap across other blockchains like the BNB Smart Chain, BNB Beacon Chain, and more.
Ps: Trust wallet isn't a recommended wallet to use as they're closed source and a product of Binance which translate to you not having any privacy as anything associate with Binance is centralized, yes Binance own trust wallet).
You should be using a non custodial wallet to store your coins and if you're worried about exchanging your coins between the same blockchain (ETH to ERC-20 tokens) or different blockchain (BTC to ETH) you can make use of instant exchanges.
List: Instant exchanges by OmegaStarScream