When I go to select download folder for a new torrent, the window is blank and all the "save to" locations are grayed out. This is recent and seems to be since an update to Windows 11 25H2. Is there a workaround for this?

I'll assume you are using the newest version, v3.42. If not upgrade and see if it still happens.
Does it happen if you try to change the location of a torrent? Or with an other pop-up window like those? Does it happen with any other program you run? Since it happened right after a Windows Update I would highly suspect something with the update messed up that window display.