It is also SO SLOW. It's so slow. Uploading images takes full seconds before they can be sent because Teams has to put them onto Sharepoint first (which itself is slow).

For those still on Teams, my condolences, here's a workaround: copy the image onto your clipboard and paste it into the textbox. It skips the uploading to Sharepoint, prevents the issue I described, and is sendable in milliseconds. Downsides: a. they're randomly ephemeral and sometimes just permanently disappear, b. no animated images - it'll just send the first frame of a GIF/APNG/etc.

And for those on macOS, that means you can get screenshots sent quickly. Ctrl-Cmd-Shift-3, Cmd-V into the text field. Send.