Two AD Forest sync to One Microsoft 365 tenant

We have Two AD Forest that need to sync to one Microsoft 365 tenant. The AD forest don't have a trust in place and can't for compliance requirements. Domain 1 has Azure AD Connect installed and is syncing users up the Microsoft 365 tenant while Domain 2 does not have Azure AD Connect installed anywhere.

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I saw a few articles about this but I'm confused by what i saw, does anyone know if it would cause any issues if we were to create a Azure AD Connect server in Domain 2 and have that sync to the Microsoft 365 tenant?