I have seen the other answers to similar problem with Brave-Browser but can't get them to work - probably because I'm not very proficient - sorry. Anyway, here is what the terminal returns:
Any help would be greatly appreciated. Thank you. Duncan
First you need to delete expired GPG key.
sudo apt-key del 4FE13824E3FFC656
Install latest GPG Key for Brave Browser repo, after you will be able to update it.
curl -s https://brave-browser-apt-release.s3.brave.com/brave-core.asc | sudo apt-key --keyring /etc/apt/trusted.gpg.d/brave-browser-release.gpg add -
Managed to find a solution - used this ref: https://unix.stackexchange.com/questions/452020/gpg-warning-unsafe-ownership-on-homedir-home-user-gnupg/452025#452025 - author: Stephen Kitt
In summary: Enter the following terminal commands: