Hi, guys! I have a similar question.
` const [tonConnectUI, setOptions] = useTonConnectUI();
const transaction = async () => {
const tx = await tonConnectUI.sendTransaction({
validUntil: 999999999, // just for tests
messages: [
{
address,
amount,
stateInit: beginCell().storeUint(0, 4).endCell().toBoc().toString("base64"),

},
]
});

console.log(tx);
}`

I use this code to make transactions on not initialized wallets, but every transaction returns to a sender. I tried to specify bounce flag, but I think I did wrong.