Most work is done by running

npx @patternfly/pf-codemods@latest webpack --fix

npx @patternfly/class-name-updater webpack --fix  

and search& replace "pf-c-" to "pf-v5-c-"
Check all "onChange=\{[^(]" to make sure that pure pf5 are using the right arguments, as they changed order, and most onChange are onChange(event,value) and not onChange(value)

Discussion here: https://community.theforeman.org/t/updating-patternfly-4-to-patternfly-5/37610