Alexey,
Again, thanks for replying.
I put
debug_backtrace_enabled = false
and restarted sssd. Still the backtrace shows up in /var/log/sssd/krb5_child.log. In both RHEL8 and RHEL9.
Is it possible that krb5_child (n version 2.9.4-x) is inheriting from another sssd.conf file section?
No, you've found a bug - there is no way to configure 'debug_backtrace_enabled' for child processes (may be with the exception of proxy_child, not sure).
I think the fix should be to inherit from the domain section (as it happens with debug_level),
Please, open a ticket upstream.