Upgrading MediaWiki can be a daunting task.
We have some detailed notes on prior upgrades like
eQuality Technology offers an automated DevOps approach to upgrades; and even running multiple versions if you require a legacy version (in a private wiki where there is less security concern). See https://QualityBox.us
- Even on a small wiki, it took 6 hours to rebuild the data when the host was only running with 2GB of RAM