No option to upgrade from 7.6.x to 8.7.x in Install-Tool Core update or upgrade wizard

Question

why the Core update shows me "No regular update available" and upgrade wizard shows me "No updates to perform!"?

I'd like to upgrade from 7.6.31 LTS to the latest 8.7.x LTS version.

Answer 1

The wizards for upgrading in the TYPO3 install tool always only performed upgrades on the same main-branch. So a change from version 7 to 8 or 8 to 9 was never considered and has to be done manually. One reason might be that also some extensions follow the same concept and it will be hard to keep the site running with automatic updates between branches.
Especially problematic would be an automatic upgrade from 8 to 9, because many things changed technically (t3_ckeditor instead of rte_htmlarea, Doctrine Dbal instead of the old TYPO3 database-layer).
So, currently there is just no option to upgrade from 7 to 8 and you've to accept to have to do that upgrade manually.
Nevertheless the upgrade-wizard is still supporting you with required database-updates and other actions to perform.

Some upgrades also require an update of PHP which would be impossible for the wizard.