Just like you say, the answer embeds sdp entry in the data entry. This unfortunately will cause a crash that I would like to apologizes for and will push to get that resolved. I would expect to see a error message from the logs ifLogPixelStreaming2WebRtc is set.
PixelStreaming2 player should not create an answer that looks like this, and should follow the answer in PixelStreamingInfrastructure/Common/protobuf/signalling_messages.proto at master · EpicGamesExt/PixelStreamingInfrastructure · GitHub
If PixelStreaming2 player from UE 5.6 is sending an answer with sdp inside data then I would like to know.
Enabling very verbose logging in both the streamer and player will log the SDP that the streamer and player use. In vscode it can be set with "-LogCmds=LogPixelStreaming2 VeryVerbose,LogPixelStreaming2EpicRtc VeryVerbose,LogPixelStreaming2WebRtc VeryVerbose,LogPixelStreaming2RTC VeryVerbose".
Regards
Eden