Thank you for reaching Microsoft Forum!
Microsoft Private Access is designed to provide secure access to services over a private endpoint within your virtual network. It's not a replacement for VPNs, which are designed to provide secure access to your entire network.
Regarding your question, Microsoft Private Access does support granting access to external guest accounts. You can use Azure AD B2B to invite external users to your tenant and grant them access to the resources that are exposed through Private Access. Also, this feature is work for Cross-Tenant Sync and Multi-Tenant Organizations.
For more readings Learn about Microsoft Entra Private Access
Hope this helps. Do let us know if you any further queries by responding in the comments section.
Thanks,
Akhilesh.
If this answers your query, do click Accept Answer
and Yes
for was this answer helpful. And, if you have any further query do let us know.