Icinga DB Web v1.2.0 (in combination with #889 here in Icinga DB) will introduce support for showing the Icinga 2 dependency configuration. Part of this feature is the ability two show root problems (introduced in this commit), which is implemented using recursive CTEs.

MySQL didn't support even basic CTEs prior 8.0. MariaDB only supports recursive ones since 10.2.2. These versions have to be documented as the new minimum requirements.