I use US TD Ameritrade and my non American wife uses non US TD Ameritrade and we live abroad. The US and non US platforms are different, with different requirements. I think TD Ameritrade is the easiest for a beginner, with intuitive charts and trading information. I haven't experienced technical issues, but found some aspects a bit frustrating. For example, it's purposefully difficult to pick the lots to sell (not FIFO method) from their TOS pc version but quite easy from their android phone app. Yet, it only works for US accounts and platform. Also, they promote 24h trading but they don't. They're 8 am to 8 pm only.
You may have legal problems trading on the US platform if you don't have a US permanent address, and a foreign IP address will let them know you're trading from abroad.