Steps to reproduce:

undertowBuilder.setSocketOption(Options.SSL_PROVIDER, "Conscrypt")
.addListener(Undertow.ListenerBuilder()
.setType(Undertow.ListenerType.HTTPS)
.setTrustManagers(<trust managers>)
.setKeyManagers(<key managers>)
)

results in the default jsse provider because only override options are used, rather than overriding the configured socket options.