I just upgraded & do some initial testing, it works well with all 3 modes of deployment (minimal, regular, upgradeable)
What I see is that when regular deployment is chosen, the cli does not offer the opportunity to run an initialization function.
When deploying regular contracts there isnโt a need to run initialization.
Any initialization could be done in the constructor of the regular contract. Though appreciate that means that a contract is different depending on whether it is upgradeable (constructor) or regular (initializer)
Automatic initializers are part of the plans for OpenZeppelin SDK 3.0 (see the SDK 3.0 Design Document)
Feedback on the Release Candidate is greatly appreciated.