The new Tag System of Twitch released yesterday night. Communities got replaced by Tags. Currently 3rd Party Software for streamers like Streamlabs Chatbot and such have not yet implemented the new tag system so you have to manually put the tags in your twitch dashboard (until the software will be updated).
Viewers can look for Fortnite and add the PVE Filter. This way you should find all the pve streamers easily (if they use the tag).
Here a short picture where and how it works: