Are there websites where I can do simple tasks like distinguishing/sorting images, writing captions, selecting correct options or other tasks I can do in my free time or mindlessly whilst also contributing to meaningful projects? Something like Google Crowdsource, although I would like to avoid registering to any privacy invading services asking for my personal info in order to contribute.
Absolutely. This has even more impact, but also a higher learning curve (OP asked to answer questions). I contribute on HOTOSM as well, it is an amazing project!