It is possible to move the member account from an Organization which has SSO enabled to an Organization which does not have SSO enabled.

Moving an account between organizations requires you to remove the account from an organization, making the account standalone, and then you accepting an invite to join another organization[1]. Please refer to the AWS blog[1] for more information about the same.

Furthermore, you do not need to make any other changes during this process.

However, post moving the member account to the different Organization, the SSO users will lose access to the account which has now moved to a different Organization.

References :

[1] https://aws.amazon.com/blogs/mt/aws-organizations-moving-an-organization-member-account-to-another-organization-part-1/#:~:text=Moving%20an%20account%20between%20organizations,and%20services%20continue%20to%20operate.