Tangentially related. I ask ebecause I know in general freelance work is not taxed, so does youtube income count as freelance income?
Freelance work is taxed in Germany, § 2 Ⅰ 1 No. 3 EStG. What is not taxed is income from a hobby, if the income is occasional and if making money is not the primary goal of the hobby. So the question has to be answered on a case by case basis.
The question arises often enough that the German Federal Ministry of Finance has published a PDF document with guidelines: "I am Influencer. Do I have to pay taxes" (German).
It lists the kind of taxes that might apply (Einkommenssteuer, Gewerbesteuer Umsatzsteuer - Income tax, trade tax and VAT).
You never pay income tax if your total (e.g. from all activities, not just the youtube stuff) yearly income is below the tax exempt allowance, § 32a Ⅰ 2 No. 1 EStG.
You have to pay trade tax if you make more than 24 500 Euro per year, § 11 Ⅰ 3 No. 1 GewStG.
If you work on youtube or other social media with the goal of making money ("Gewinnerzielungsabsicht") you have to do a "Umsatzsteuervoranmeldung" (VAT declaration). That is, if you write invoices to your sponsors, you charge them VAT, which however does not belong to you - you collect it and pass it on to the state. If you buy stuff for your social media work, you can deduct the VAT you pay for that from the sum you pass on. Note that you have to do the declaration even if you do not actually owe anything.
If making money is not your primary goal, and the revenue is small and irregular, then you do not need to pay taxes on your social media income. However there is no fixed amount that constitutes "small" income, that depends to some extent on your tax office (also if you do not pay taxes for it, you cannot deduct business cost from tax bill). As mentioned in a comment, monetizing your videos via ad views would be almost certainly considered a Gewinnerzielungsabsicht (since the idea is making a regular income), getting a bit of free stuff in return for a video not necessarily.
This is not legal advice, but personally I would not bother to report a few hundred that I make on the side over the year, especially if I get the money in non consecutive months (but then in my case a few hundred would not make a difference in any case). But if your income is high (thousands rather than hundreds) or regular (e.g. monthly for most of the year) you need to declare it on your taxes.