The file share setup we currently have still uses a managed domain through AD housed on 2 Azure VM DCs. We connected our on-premises network to Azure with a S2S VPN tunnel, and our remote users connect to the network using P2S tunnels from the Azure VPN Client. We have a couple file shares configured at our offices on Windows 10 machines.
I was worried the file shares would begin failing if we moved our remote users from Hybrid Azure AD-joined machines to Azure AD-joined machines, but as long as the user is configured in AD, when they connect to the VPN they're still able to access the file shares even though the machines are not configured in AD. The file shares themselves are on machines that are configured in AD, but the laptops remote users connect with are not, they're only in Azure AD. This setup also works with file shares configured on the Azure VMs.
Perhaps we will fully migrate away from AD one day, but as an interim step, this allows us to stop dealing with clunky Hybrid Azure AD-joined machines for our remote users.
Hopefully this workaround helps you figure out a solution for your tenant.