[akramhussein]

Facebook groups/Reddit are quite useful. Search for something related and gently drop a link with explanation, but don't spam people and multiple groups in one go - go step by step to test reception. If you are solving someone's problem they are usually quite receptive to trying things.

[Aldina]

Thanks for the suggestion. Actually I find some subreddit's, but I coudn't find Facebook groups relevant for beta testing,...I will search more.