This question resolves to YES if I can both receive and send:

• Text messages AND

• Voice messages AND

• Pictures

in a 1:1 chat between accounts on WhatsApp and Signal on or before March 6th without having to sign up to a third party bridging service.

For context, the EU's Digital Markets Act has entered into force on November 1st, 2022.
Among many other things, it requires basic interoperability between Messaging Services, 3 months after they have been asked to implement it.