What were you trying to do that didn't work?

Trying to execute yum update --security fails with conflicts when having some multiarch packages:

# yum update --security
[...]
Error: 
 Problem: zlib-1.2.11-21.el8_7.i686 from @System  does not belong to a distupgrade repository
  - cannot install both zlib-1.2.11-25.el8.x86_64 from os and zlib-1.2.11-21.el8_7.x86_64 from @System
  - cannot install both zlib-1.2.11-25.el8.x86_64 from os and zlib-1.2.11-21.el8_7.x86_64 from os
  - cannot install the best update candidate for package zlib-1.2.11-21.el8_7.i686
  - cannot install the best update candidate for package zlib-1.2.11-21.el8_7.x86_64
(try to add '--allowerasing' to command line to replace conflicting packages or '--skip-broken' to skip uninstallable packages or '--nobest' to use not only best candidate packages)

Please provide the package NVR for which bug is seen:

libdnf-0.63.0-17.el8_9.x86_64
libsolv-0.7.20-6.el8.x86_64

How reproducible:

Always

Steps to reproduce

1. Update a RHEL8.9 system to latest, without having i686 packages initially

   # yum -y update

2. Install a few i686 non-latest packages including an old glibc

   # yum -y install glibc-2.28-225.el8.i686 libldb-2.6.1-1.el8.i686 zlib-1.2.11-21.el8_7.i686 zlib-devel-1.2.11-21.el8_7.x86_64

3. Try executing security update

   # yum update --security
   [...]
   Error: 
    Problem: zlib-1.2.11-21.el8_7.i686 from @System  does not belong to a distupgrade repository
     - cannot install both zlib-1.2.11-25.el8.x86_64 from os and zlib-1.2.11-21.el8_7.x86_64 from @System
     - cannot install both zlib-1.2.11-25.el8.x86_64 from os and zlib-1.2.11-21.el8_7.x86_64 from os
     - cannot install the best update candidate for package zlib-1.2.11-21.el8_7.i686
     - cannot install the best update candidate for package zlib-1.2.11-21.el8_7.x86_64
   (try to add '--allowerasing' to command line to replace conflicting packages or '--skip-broken' to skip uninstallable packages or '--nobest' to use not only best candidate packages)

Expected results

Updates properly

Actual results

Fails with no much hint on exact reason