Nexctcloud 18.0.0, File Sharing 1.10.1
Can not web open shared files. Problems with all types (photo, video, text). When I click to name of files - files will download and only download option is avaliable. If I allow edit - I can remove files, but not can open in browser.
Common file opening (not from shared link) works fine.
Im having the same issue since upgradig to nextcloud 18. I use the share method for customers to select images for retouch. Before they could browse the images and preview, now they have to download to se larger preview and only see thumbnail.
18.0.1 update and reboot does not help. 
18.04 will be solve or manual now.
Im have the same issue after update to 18.0.3 version
From the Bugtracker: enable Federated sharing in the Admin Settings.
