iphone se3 dual sim active

See -> Use Dual SIM on iPhone -> Use Dual SIM on iPhone – Apple Support (UK)

so that I can receive and make calls without manual switching between the two sim cards.

No, the iPhone SE 3rd gen comes with a Nano SIM slot and a built-in eSIM. So you can insert a physical SIM and activate the eSIM for a Dual SIM experience.

so the physical sim + e-sim supports Dual-Sim-Active (DSA),

Yes, you are right.

Thank you for your feedback and you're welcome.