Is there any way to print plain text of request and response when connecting to wss endpoint ?

[AlwaysNoobCoder]

I can use wireshark + export SSLKEYLOGFILE=~/.ssl-key.log to decrypt packets for browser.

but don't know how to do with websocat.

[vi]

You can build WebSocket connector manually using overlays, then also use log: overlay for debug printing: https://github.com/vi/websocat/blob/master/moreexamples.md#at-http-and-websocket-protocol-level