You can install the server without activating it, but you will not be able to use it. And you might also be unable to generate activation credentials if you haven't activated previous instances in the same tenant. MFA Server has not been supported for new deployments since few years now, and last week at Ignite Microsoft announced the deprecation plan:
In September 2022, Microsoft announced deprecation of Azure AD Multi-Factor Authentication Server. Beginning September 30, 2024, Azure AD Multi-Factor Authentication Server deployments will no longer service multifactor authentication (MFA) requests, which could cause authentications to fail for your organization.