What I did:
Tried embedding the image from this post on Hexbear: 
Expected result:
Image is embedded
Actual result:
More info: These hosts are whitelisted for embedding images on Hexbear:
- chapo.chat
- discuss.tchncs.de
- hexbear.net
- i.imgur.com
- jlai.lu
- lemm.ee
- lemmy.ml
- lemmy.world
- lemmygrad.ml
- mander.xyz
- pathfinder.social
- possumpat.io
- test.hexbear.net
- toots.matapacos.dog
- ttrpg.network
- www.hexbear.net
But in the case of toots.matapacos.dog, assets.toots.matapacos.dog should be whitelisted instead.