Can I create users manually for temporary access or demos?

I want to onboard a few users which are not employees of my company on my Foundry enrollment, so that they can see some demo and poke around by themselves to show them the product we built for them.

Building an integration with their own SAML/IDP would be too heavy for this purpose, as this is only intended to be temporary (for example, a few days just to showcase a use-case or workflow).

How can I create such temporary accounts ? How can I let those users login with those accounts ?

Internal realm users are almost universally disabled following Palantir Information Security best practises. The best approach currently is to give the users accounts in CentralAuth (docs). (This will be the case until the Palantir-developed self-service user directory is available for general use). Unfortunately, getting users CentralAuth accounts must be done by Palantir and is not self-service.