If it is an LSE-listed company, there is no way around it. But the ETFs (even UK-based ones) do not charge stamp duty.
They are not available yet, more details from @JamieP on that:
https://community.freetrade.io/t/will-freetrade-offer-aim-shares/2434/2?u=vlad
Absolutely right, you will not have any additional duties for the US stocks except the FX rate + 0.5%.
See detaailed calculations on what it means here.