Couch surfing https://www.couchsurfing.com/  (Trade-Free)
https://www.trustroots.org/ (Trade-Free)

https://www.bewelcome.org/ (trade-free)

Find accommodation in exchange for help with a project:
https://www.volunteersbase.com/
You have a place to stay in exchange for chatting with the host:
https://www.talktalkbnb.com/

WWOOF http://wwoofinternational.org/  (charges for registration)

Workaway  https://www.workaway.info

https://github.com/Darnok11/Freelife/blob/master/README.mdFind free accommodation by bikehttps://www.warmshowers.org/