Secure Boot on RHEL

My SCST service does not want to come up on an RHEL 8.5 when Secure Boot is turned on; even after I have gone to the UEFI menu and registered the keys using MOK menu per README instructions here: https://github.com/bvanassche/scst/blob/master/README.module-signing

I get the following error:
● mediator-scst.service
Loaded: loaded (/etc/systemd/system/mediator-scst.service; enabled; vendor preset: disabled)
Active: failed (Result: exit-code) since Wed 2021-12-08 10:26:33 EST; 1 day 22h ago
Process: 7320 ExecStart=/etc/init.d/scst start (code=exited, status=5)

Dec 08 10:26:33 scs000040681 systemd[1]: mediator-scst.service: Service RestartSec=100ms expired, scheduling restart.
Dec 08 10:26:33 scs000040681 systemd[1]: mediator-scst.service: Scheduled restart job, restart counter is at 5.
Dec 08 10:26:33 scs000040681 systemd[1]: Stopped mediator-scst.service.
Dec 08 10:26:33 scs000040681 systemd[1]: mediator-scst.service: Start request repeated too quickly.
Dec 08 10:26:33 scs000040681 systemd[1]: mediator-scst.service: Failed with result 'exit-code'.
Dec 08 10:26:33 scs000040681 systemd[1]: Failed to start mediator-scst.service.

My System's Info:
cat /etc/redhat-release: Red Hat Enterprise Linux release 8.5 (Ootpa)
mokutil --sb-state: SecureBoot enabled
modprobe scst && modprobe -r scst:
modprobe: FATAL: Module scst not found in directory /lib/modules/4.18.0-348.2.1.el8_5.x86_64

Please, note that I have tried this on various RHEL OSes and each one is giving me a different result! I will be happy to see it working on the latest OS release of RHEL, which is 8.5!

Any help/hint is greatly appreciated - or if this is a bug (maybe the README file need be updated), please, address it.