I can confirm the same problem and the "Scroll Lock" workaround worked here too. I'm using my system with English language but the keyboard is the BR-ABNT2. I tried with different drivers of Nvidia and with Noveau, no difference. I'm using ubuntu 20.04.1 LTS.
-- You received this bug notification because you are a member of Ubuntu-X, which is subscribed to xkeyboard-config in Ubuntu. https://bugs.launchpad.net/bugs/1895486 Title: [media-keys] Fn media keys with lag slow/delay on Gnome with "Scroll Lock" keyboards To manage notifications about this bug go to: https://bugs.launchpad.net/gnome-shell/+bug/1895486/+subscriptions _______________________________________________ Mailing list: https://launchpad.net/~ubuntu-x-swat Post to : [email protected] Unsubscribe : https://launchpad.net/~ubuntu-x-swat More help : https://help.launchpad.net/ListHelp

