What Encrypted Communication App To Use?

In an effort to attempt to remain as anonymous as possible while communicating with my colleagues for work purposes, I have poured over the extensive list of privacy focused messenger apps currently on offer, and have whittled the selection down to a handful. But from here, I'm wondering what the community suggests for "ultimate" privacy in the p2p communication department.

We are using a privacy focused OS on degoogled phones, with no sim cards, using proxys over Wifi, manually scrubbing …

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