Answer: A remote internal audit is possible, provided that required evidence of conformance does not need the physical presence of the auditor on-site. So for a precise evaluation of the impact you need to identify the volume of on-site related evidence you need (probably most of them will be related to physical security).
For example, to audit the conformance of a laptop used when working from home, the auditor can audit the laptop's access logs against the authorized access rights (by auditing corporate servers that host the accessed information systems), or he can remotely access the laptop to audit its settings.
2 - What is the way to handle it?
Answer: For situations where it is necessary to make on-site observations (e.g., to audit the conformance of physical security controls), the audited company should provide evidence of such controls remotely (e.g. through photographs, plans, maps, etc.).