Even if you don't register as sole proprietor you need a PAN card to file income tax return and also YouTube will ask for your PAN card to verify.
If you want promote yourself as a brand you can make a sole proprietor but there is no such need to compulsorily have a sole proprietorship.
Now the income which you earn from YouTube or affiliated marketing you can show it as income from other sources if it's your part time income and if it's your full time work and only source of income then you can even show it as professional income and in the beginning when you don't have much income i.e. your annual receipt is below 50lakh you can file income tax return u/s 44ADA i.e. presumptive section. And show 50% of gross receipts as your income and file return of income.
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All the best for your YouTube channel.