Messages cannot be decrypted [DC 1.2.15, failed: PGP: MissingKey]

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The message in the screenshot is showing that incoming message has anonymous Key IDs (0x000…000). Old Delta Chat cannot decrypt such messages:

PSA: Known interoperability problem in chatmail core <1.160.0

While trying to enable wildcard OpenPGP Key IDs, we have discovered incompatibility in core versions <1.160.0. Key IDs are constructed as the hash of the key fingerprint truncated to 64 bits. They are normally transmitted in plaintext in OpenPGP messages so recipients can identify the PKESK (Public Key Encrypted Session Key) that is intended for them instead of trying to decrypt each PKESK. The disadvantage of this is that part of the key fingerprint is transmitted in plaintext. Because of this…