You could half-ass it like many (most?) vendors seem to do. You can always tell they've shoehorned their on-prem product into a SaaS offering when they ask you

You could half-ass it like many (most?) vendors seem to do. You can always tell they've shoehorned their on-prem product into a SaaS offering when they ask you to port forward on your firewall to your LDAP server and don't support SAML/OAuth/OIDC. Bonus points when they can't give you a dedicated per-costumer IP or range to whitelist. More bonus points if they can't give you any to whitelist at all without a bunch of internal communication/work (shared or not).