yum/dnf fails to apply security updates, reporting conflicts "cannot install both packageA_relX.i686 and packageA_relY.x86_64" and the like

Issue

• Trying to apply security updates on the system, errors are returned, as shown in the example below:

  # yum update --security
  [...]
  Error: 
   Problem 1: glibc-gconv-extra-2.28-225.el8_8.6.i686 from @System  does not belong to a distupgrade repository
    - cannot install both glibc-gconv-extra-2.28-236.el8.7.x86_64 from os and glibc-gconv-extra-2.28-225.el8_8.6.x86_64 from @System
    - cannot install both glibc-gconv-extra-2.28-236.el8.7.x86_64 from os and glibc-gconv-extra-2.28-225.el8_8.6.x86_64 from os
    - cannot install both glibc-gconv-extra-2.28-225.el8_8.6.x86_64 from os8eus and glibc-gconv-extra-2.28-236.el8.7.x86_64 from os
    - cannot install the best update candidate for package glibc-gconv-extra-2.28-225.el8_8.6.i686
    - cannot install the best update candidate for package glibc-gconv-extra-2.28-225.el8_8.6.x86_64
   Problem 2: nss_db-2.28-225.el8_8.6.i686 from @System  does not belong to a distupgrade repository
    - cannot install both nss_db-2.28-236.el8.7.x86_64 from os and nss_db-2.28-225.el8_8.6.x86_64 from @System
    - cannot install both nss_db-2.28-236.el8.7.x86_64 from os and nss_db-2.28-225.el8_8.6.x86_64 from os
    - cannot install both nss_db-2.28-225.el8_8.6.x86_64 from os8eus and nss_db-2.28-236.el8.7.x86_64 from os
    - cannot install the best update candidate for package nss_db-2.28-225.el8_8.6.x86_64
    - cannot install the best update candidate for package nss_db-2.28-225.el8_8.6.i686