A connection error usually means there is a server side error, can you check the logs/output.log when uploading an image in the composer.

When user load avatar from imgur : error this operation is insecure on firefox you have this error : [image: 1610712481315-2021-01-15_08h56_42.png] on chrome [image: 1610712614183-2021-01-15_09h32_55.png] when user upload an image in a post or for avatar, there is this error [image: 1610712650654-2021-01-15_08h56_13.png]