Re: Migration from 5.5.31 to 8.0

[Peter Brawley]

Good overview of upgrade options & advice at https://www.percona.com/blog/2014/09/19/mysql-upgrade-best-practices/

You mustn't try to jump from 5.5 to 8.0---it'll fail on cascading incompatibilities. You need to step through each major version.

I think that's an argument for creating a new mysql instance that starts with a copy of 5.5, step through upgrade-and-debug to 5.6, 5.7 then 8.0, and when no more bugs can be found in the new 8.0 instance then on the slave change master to that new 8.0 instance.