KeePassXC 2.6.4 addons failure on Firefox and Chrome/Brave /Ubuntu 20.04 and 20.10

Solution 1:

Issue occurred because snap version of KeePassXC and Brave browser. To install unsnapped KeePassXC version: Add PPA to system's software source:

sudo add-apt-repository ppa:phoerious/keepassxc
sudo apt-get update
sudo apt install keepassxc

unsnapped version of Brave browser:

sudo apt install apt-transport-https curl gnupg
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 -
echo "deb [arch=amd64] https://brave-browser-apt-release.s3.brave.com/ stable main" | sudo tee /etc/apt/sources.list.d/brave-browser-release.list
sudo apt update
sudo apt install brave-browser