DPKG add and list architectures:
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Add arch for dpkg example:
sudo dpkg --add-architecture i386

List architectures for dpkg:
dpkg --print-foreign-architectures

list only one arch for apt list example's:
deb [arch=powerpc] http://old-releases.ubuntu.com/ubuntu yakkety main universe multiverse restricted
deb [arch=amd64] http://dl.google.com/linux/earth/deb/ stable main

Remove an architecture:
sudo apt-get purge ".*:i386" --allow-remove-essential
sudo dpkg --remove-architecture i386

Sources:
https://branden-g.ca/Notes/Tech_Help/Linux_Repair/Linux_Apps_Setup/Install_Linux_apps_and_drivers/Google-earth-ppa.txt
https://askubuntu.com/questions/560636/dpkg-error-unknown-option-add-architecture
https://askubuntu.com/questions/852115/how-to-check-if-dpkg-architecture-list-has-all-the-architectures#852120
https://superuser.com/questions/714391/how-do-i-remove-all-i386-architecture-packages-from-my-debian-installation

Date: October 5th 2023.
Update 1: November 24th 2025 (for remove isa)