Thanks @KitsuneNoBaka
@betty and for mullvad, same thing:
sudo http_proxy=http://127.0.0.1:8082 https_proxy=http://127.0.0.1:8082 curl -fsSLo /usr/share/keyrings/mullvad-keyring.asc https://repository.mullvad.net/deb/mullvad-keyring.asc
then:
echo "deb [signed-by=/usr/share/keyrings/mullvad-keyring.asc arch=$( dpkg --print-architecture )] https://repository.mullvad.net/deb/stable stable main" | sudo tee /etc/apt/sources.list.d/mullvad.list
and
sudo apt update
sudo apt install mullvad-browser
For Brave, i had no trouve with export all_proxy=http://127.0.0.1:8082