The screenshot you put seems to be from the SimpleRequestFactory constructor. That is the default timeout for the httpClient, but there is also a timeout per request, which can be set(see line 314: request.idleTimeout(timeoutSeconds > 30 ? 30 : timeoutSeconds-1, TimeUnit.SECONDS);).
How are you using the rest client? You should be able to do something like this to change the timeout:
The rest client needs to be written from zero. We need to upgrade to jetty 12 and all APIs changed. Furthermore, since on Java 21 we now have a builtin http client that we can utilize. So the rest client specifically might need a complete open heart surgery