Currently, the upload UI turns grey when an attachment upload finishes.

If you don't notice the green notification text that briefly appears and don't catch on the green checkmark icon, it feels like the upload crashed, and that something is still going on because:

• the green progress bar is still there
• no text says that the upload succeeded

I believe the progress bar should be removed and a permanent text should make it clear the upload finished. In addition to this, I would remove grey line at the bottom with the percentage, the size, the speed and the estimation time remaining that shows "00:00:00", they reinforce the feeling that something is not finished, are confusing and not useful. This text's contrast is too low anyway.

It can be useful that the "succeeded!" text says the time the upload took to complete and the average speed. Like: "The upload succeeded in 00:00 (N MiB/s)

See the attached screen record to follow this description.