Fresh install, converting from cpanel, but EOL php and mysql

you can't do this. there will be mysql8 or mariadb 10.6 by default, not sure you can install lower than mysql 5.7 and maria 10.4.
you can try convert mysql DB on any other server with needed version. But in my practice - websites on PHP 5.2 works fine on new versions. but better test it - try any shared hosting with DA and new versions, add IP of new hosting to hosts-file and test how website will work without touching working version.