This extension adds a new CType for an A-Z index with Links to the related pages. This will insert the keyword index on the page. See example page at https://www.mehrwert.de/meta/a-z-index/
For details see the manual at https://docs.typo3.org/typo3cms/extensions.
This upgrade for TYPO3 8.7 compatibility is to be considered as untested and works for my clients purposes. No further tests conducted.