Taken from comment 13819076.

Update configuration to manually enable the jacc in standalone.xml (or the file where eleytron is installed).

We can do this by either of the two ways :
1. Open the management Cli and provide the command

/subsystem=elytron/policy=jacc:add(jacc-policy={})

2. Add the below tag under elytron subsystem.
<policy name="jacc">
<jacc-policy/>
</policy>

With this RHSSO with elytron works as usual.