i don't know the Rentberry project you mentioned but if they don't have the telegram or telegram their group has been deleted, maybe they are a project scam.
but it looks like Rentberry has given you the answers you need.
Hi everyone,
Feel free to follow us in
Official Announcement Channel where we post the updates:
https://t.me/RentberryNewsWe have recently released the Co-Signer network feature. Feel free to check it out and participate. You may read more information on this new feature in our
Help Center:
https://help.rentberry.com/co-signer-network-help Also, we have released the apps on
iOS and
Android.
If you are in Kyiv, we welcome everyone who wants to visit us in our office.