Hi!
I've recently started working on questionnaires for my PhD research work. The problem that I've been facing is that it's really difficult to find a place to post questionnaires!
This forum is really helpful and cooperative and I hope to get good responses to my questionnaire here (posted in the pinned 'Post your surveys' topic).
However, would you guys know of any other places where surveys/questionnaires can be posted?
Thank you for your help!

Search Facebook Groups from your university or related to your topic.

What's in your ethics approval? That will determine where you can post links to surveys.

Did you account for social media, forums etc? What kind of questionnaire is it? What kind of participants are you looking for?

Depending on the above, you can get into contact with moderators for specific forums that might have the kind of participants you are looking for, as well as organisations to pass through their respective networks. But, 1), this needs to be in your ethics approval before you can go forward, and 2), always get mod approval before posting on sites like forums (apart from here obviously) so it doesn't get deleted or you don't get a nasty email and a potential breach of your ethics obligations.