There was a Falcon 9 launch from Florida last night injecting Starlink satellites into a 53 deg orbit and later there was a second stage de-orbit burn but this observation doesn’t seem to be consistent with that. It is a bit of a coincidence though and I don’t know what else it could be.
On my all sky camera this starts out as a very bright point moving out of shadow and then expands into a fuzzy disk with a point in the centre.
My daughter (non-astronomer) saw and picked up this this circular cloud during twilight on 21st April 21.31h BST moving eastwards across the sky. I guess it was also a fuel dump, but much more entertaining to suggest it was a toilet dump from the ISS!