use stderr instead of /dev/stdout that may be unaccessible in change user context.
version up : stunnel 4.56.

disable FIPS explicitly, otherwise stunnel fails to start with the following output :

Threading:PTHREAD Sockets:POLL,IPv6 SSL:ENGINE,OCSP,FIPS
Reading configuration from file etc/stunnel.conf
FIPS_mode_set: F06D065: error:0F06D065:common libcrypto routines:FIPS_mode_set:fips mode not supported
Line 5: "[remote]": Failed to initialize SSL