Maybe off-topic answers since you probably specifically meant fediverse communities, but here’s my thoughts:

• Local Buy Nothing groups can be a great way to keep things in use and out of landfills.
• I would think any craft communities might be a great way to get general ideas.
• I see what you did there.

Just my thoughts, fwiw.

You may also be interested in:
!reuse
!freecycle
!thrifty
!frugal

I know this is a couple days old but just popping in to suggest [email protected]