If you are using a US LLC, then the account will be opened through IBKR US office. If you are a non US resident in that US LLC, then besides a 30% withholding tax (as declared on your W8-BEN) on dividends, all capital gains (short term and long term, as well as crypto) are not subject to tax (though form 5472 should be︀ filed annually).
To date, the US is non CRS compliant so the IRS does not︁ share that information with your country of residence. For non US residents, the US is︂ still cost effective, as the setup costs are far cheaper than many other alternatives.