How to fix E: Package 'package:i386' has no installation candidate in APT

First, register i386 as a supported architecture on your system:

sudo dpkg --add-architecture i386

Verify the architecture is now enabled:

dpkg --print-foreign-architectures

You should see "i386" in the output. If you see nothing, the previous command had an issue.

Refresh the apt package cache to include i386 packages from all repositories:

sudo apt update

Watch for any error messages about unsupported architectures. If you see warnings like "repository does not support i386", you'll need to fix those repository configurations in the next step.

Some repositories may explicitly restrict packages to amd64. Check your sources:

grep -r "arch=" /etc/apt/sources.list*

If you see entries restricted to amd64 only, like:

deb [arch=amd64] http://example.com/ubuntu focal main

Edit the file to include i386:

sudo nano /etc/apt/sources.list

Change to:

deb [arch=amd64,i386] http://example.com/ubuntu focal main

For sources in /etc/apt/sources.list.d/*.sources, add Architectures: amd64 i386 under the Sources section.

After editing, run:

sudo apt update

Verify the package actually exists for i386:

apt-cache search package-name | grep i386
apt-cache policy package-name:i386

The policy output shows all available versions and their source repositories. If no i386 version is listed, the package may not be available for 32-bit systems in your repositories.

Once i386 is enabled and package lists are updated, install the package:

sudo apt install package-name:i386

For example, to install 32-bit libc6:

sudo apt install libc6:i386

If you encounter dependency conflicts, apt will suggest solutions. You may need to install matching amd64 versions or update other packages.