I got a list of all the rejected maintenance requests for packages with name "yast2*" in 2021. Then I manually filtered out those which IBS projects are currently in sync with the repository branch (since I assume there was a follow-up request that fixed the problem).
These ones still remain to be fixed. Note not all of them correspond to the problem building in i586, there are also other kind of problems.
In fact, I'm not even sure if this list includes all the maintenance updates blocked by the i586 problem.
Out of sync in SLE-15-GA * yast2-pkg-bindings
Out of sync in SLE-15-SP1 * yast2-pkg-bindings
Out of sync in SLE-15-SP2 * autoyast2 * yast2-network * yast2-packager
Out of sync in SLE-15-SP3 * autoyast2 * yast2-add-on * yast2-country * yast2-installation * yast2-theme * yast2-network * yast2-packager * yast2-schema
Branches are not matched to IBS projects as expected * yast2-migration - Looks like it was not correctly branched into SLE-15-SP3 back then * yast2-rear - Problems due to branches when submitting to SLE-12-SPX (yes, 12) * yast2-python-bindings - Branches are messy