Ash Postgres: How to detect change when updating nullable column from NULL to non-NULL value without using atomic_update?

I couldn’t upgrade past 3.22.2. Starting with 3.23.0 (also with 3.23.1) an embedded resource (the only one so far) doesn’t work anymore:

(Protocol.UndefinedError) protocol Jason.Encoder not implemented for Xyz.Recordings.TransferSettings (a struct), Jason.Encoder protocol must always be explicitly implemented.

I have to postpone further investigation until Tuesday.

In case it matters: I am not using ash_json_api.