I use both Interactive Brokers and Internaxx.
IB is a little cheaper than Internaxx for trading costs.
I had no problems opening these accounts from within the UAE.
With both I am able to buy Irish Domiciled ETF’s (Allowing a reduced dividend withholding tax of 15% instead of the 30% when buying US domiciled funds) on the London Stock exchange from providers like Vanguard and iShares in multiple currencies.
I have built a low cost portfolio of index funds with an annual expense ratio of 0.22% plus my buying costs which I help to reduce by investing quarterly.
There is a ton of information out there if you want to research it or you could just read one of Andrew Hallam’s books to help get you started.