That's not true at all. Most vendors, if you make them specify it in a contract, will provide you with a way to export the hashes and some vendors support impo

That's not true at all. Most vendors, if you make them specify it in a contract, will provide you with a way to export the hashes and some vendors support importing users with existing hashes. Okta in particular will import existing hashes. My company moved to Okta from a home grown solution in 6 months and I suspect after the work we put in place to facilitate that would allow us to move somewhere else in even less time as long as they supported importing hashes.