Can an 830 with 8.1 still be upgraded to windows 10 mobile?

I bought a used 830 and it has Windows 10 on it, it was described as mint and it is, except that when I received my first phone call the ear speaker is inoperative. I was wondering if it could be a W10M thing and I was considering restoring to 8.1

My question is can a phone with 8.1 still be upgraded to W10M seeing as MS dropped the OS?

If I can get a refund I want to get it back to W10M, or just keep it on 8.1 if it corrects it. I like the phone but I need the ear speaker working,...

Thanks

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