You can register pretty much any domain you want, as long as its available.
However, you should think carefully about the domain name you choose, as it will represent you for a long time to come.
For example, if you are a local business, a local country domain may make more sense, because then anyone who sees your website domain will then know that you are local.
If you had a .com domain, they might not consider you as they will presume you are an international company.
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