Strange buzzing/hissing engine noise

You can but only for a few seconds it's a pretty rough thing to do. Best to use the stethoscope idea above to isolate the noise with the belts on.

I will try that trick then.

Is it recommended to use a pair of original Suzuki belts or are there some good aftermarket brands (which ones)?

The thing is that a few aftermarket belts which I found (Japanparts, Nipparts, etc. - no big brands) are like 7-8 times cheaper than original belts. These aftermarket ones are dirt cheap, like 5 EUR per belt.

So I'm wondering which ones to purchase. Does any high-level aftermarket brand make these belts and pulleys etc.?

No eBay APP ID and/or Cert ID defined in Kunena configurationThere is a cheap way to bypass the A/C compressor (if thats whats failed). You can use a 4PK850 belt to miss out the compressor on that run of belt as its shorter and doesnt foul on anything. I have found no great difference with branded or dealer belts from the cheap ones, so cheap it is

I only know about A/C because mine has failed. There is a magnetic clutch in the pulley part of the compressor. On my grey jimny the bearings failed in the pulley so i bypassed it. In my red jimny the clutch has failed instead and its constantly engaged (can see frosting on the pipes when A/C is switched off so is still engaged, but fan doesnt run except when A/C switched on).
A friend had a spare A/C compressor from a ignis sport, which has the same pulley/clutch arrangement. i found you can undo the allen bolt in the centre of the pulley and remove/swap the pulleys as a spare part (much easier than the manual shows about rebuilding). This can be done on the car provided the radiator is removed (coolant is much easier to replace than the refrigerant gas!)