Just to be clear: that is not what the original question is. OP is not asking about tax on cashing out an investment. OP has for 10 years been︀ running a business and doing work, for which he was paid in crypto. That income︁ was never declared and no tax paid on it. So now OP has a bunch︂ of crypto that he wants to cash out. My whole point is that moving to︃ UAE isn't technically going to undo 10 years of tax evasion.
Your question is the︄ age old "What tax do I pay on cashing out a crypto investment?", to which︅ the answer is it depends on where you live and what local law says there.︆ Some tax it, some don't. Those who tax it may tax it differently depending on︇ whether they consider crypto a currency, an asset, a security, or something else.
TBH, I think the reason for the confusion in this thread is that is a lot of people haven't fully understood the question.
People are answering the question: "Is there tax on selling crypto in UAE?"
When the question actually was: "I have earned︀ income for 10 years, not declared or paid tax on it, moved to UAE recently,︁ and now plan to cash out the income. Does my former home country have legal︂ grounds to prosecute me for tax evasion?" Which, yes, it does. It probably won't happen,︃ though, if OP plays his cards correctly.