How to fix W: Skipping acquire of configured file 'main/binary-i386/Packages' as repository doesn't support architecture 'i386' in APT

Run these commands to see which architectures your system is configured for:

dpkg --print-architecture
dpkg --print-foreign-architectures

Expected output:
- dpkg --print-architecture shows your primary architecture (usually amd64)
- dpkg --print-foreign-architectures shows additional architectures (if empty, no i386 is registered)

If the second command returns i386, that's why you're seeing these warnings.

Verify whether you have any 32-bit packages installed:

dpkg -l | grep i386

If the output is empty or minimal, you don't need the i386 architecture.

Common reasons to keep i386:
- Running Wine for Windows applications: wine, wine32, wine32-tools
- Playing games with Steam (older games may require i386 libraries)
- Running legacy 32-bit applications

If you see packages:

ii  libqt5gui5:i386         5.15.2+dfsg-5ubuntu2:i386   amd64   Qt 5 GUI library
ii  libc6:i386              2.35-0ubuntu3.1:i386        amd64   GNU C Library

Then keep the i386 architecture. If you see nothing, proceed to removal.

If you don't need 32-bit packages, remove the i386 architecture:

sudo dpkg --remove-architecture i386
sudo apt update

This will:
1. Remove i386 from the list of foreign architectures
2. Stop APT from looking for i386 packages
3. Eliminate all 'i386 not supported' warnings

Verify it worked:

dpkg --print-foreign-architectures
# Should output nothing or not show i386

Note: Do NOT remove i386 if you have 32-bit packages installed. If you try, apt will warn that packages depend on the i386 architecture.

If you want to keep i386 support for legitimate reasons but eliminate warnings for repositories that don't support it, specify the architecture explicitly in your sources list:

Edit your sources (Ubuntu/Debian):

sudo nano /etc/apt/sources.list

Original line (requests both architectures):

deb http://archive.ubuntu.com/ubuntu/ jammy main universe

Change to (only request amd64):

deb [arch=amd64] http://archive.ubuntu.com/ubuntu/ jammy main universe

For third-party repositories in sources.list.d:

sudo nano /etc/apt/sources.list.d/docker.list

Add [arch=amd64] to each repository line that doesn't support i386:

deb [arch=amd64] https://download.docker.com/linux/ubuntu jammy stable

Save and update:

sudo apt update

This approach keeps i386 architecture available for packages that need it while preventing warnings from repositories that don't support it.

If you're using Wine for Windows compatibility or Steam with older games, you need the i386 architecture:

For Wine (32-bit game support):

# i386 is required for Wine
# Keep the architecture and just ignore the warnings
# They don't affect functionality

For Steam:
Steam may require certain i386 libraries even on 64-bit systems. Keep i386 enabled if you're running Steam games.

To minimize warnings while keeping i386:

Edit sources to specify only amd64 for repositories that don't support i386:

sudo nano /etc/apt/sources.list

Add [arch=amd64,i386] only to repositories that you know support both:

# Supports both amd64 and i386
deb [arch=amd64,i386] http://archive.ubuntu.com/ubuntu/ jammy main

# Only amd64 (prevents i386 warning)
deb [arch=amd64] http://security.ubuntu.com/ubuntu jammy-security main

Then run:

sudo apt update

After making your changes, run apt update to verify the warnings are gone:

sudo apt update

Expected output (no i386 warnings):

Hit:1 http://archive.ubuntu.com/ubuntu jammy InRelease
Hit:2 http://archive.ubuntu.com/ubuntu jammy-updates InRelease
Reading package lists... Done
Building dependency tree... Done

If warnings persist:
- Check that you saved the sources.list file
- Make sure all affected .list files in /etc/apt/sources.list.d/ are updated
- Verify i386 is actually removed with: dpkg --print-foreign-architectures

To see which repositories have issues:

sudo apt update 2>&1 | grep -i "skipping.*i386"

This shows exactly which repositories are causing the warnings.