Using Chrome browser on Windows 10 PC, my Trello keyboard shortcut "F" stopped working to bring up Filter mode. I should say, I had to type uppercase F to get it.
I discovered it was the Evernote Web Clipper eating the shortcut key before Trello could see it, at least the lowercase F.
I don't use the Evernote keyboard shortcuts to save pages, so I disabled that extension's keyboard shortcuts and it fixed my unresponsive lowercase F in Trello. It now brings up the Filter screen again.
Hope that helps someone else.