Your system information

• Steam client version (build number or date): Jul 30 as 00:13:42
• Distribution (e.g. Ubuntu): Fedora 34
• Opted into Steam client beta?: Yes
• Have you checked for system updates?: Yes

Please describe your issue in as much detail as possible:

I tried to move a Proton Game and it failed right away. But i can move games that don't use Proton.
The old manager was able to move proton games.

Steps for reproducing this issue:

1. Menu "Steam"
2. Settings
3. Downloads
4. Steam Library Folder
5. (New Download Manager opens)
6. Select a game
7. Click move
8. select the target and confirm
9. and fail ...