You can hardmod to unbrick, but afaik you have to unbrick before you can use a hardmod to get the OTP hash. And once you hardmod to unbrick, at that point it would probably be easier to just go with the software version of dumping the OTP. But that is purely speculation based on my VERY limited knowledge of the 3ds hardware and software.
Edit: I know you would be flashing a modified NAND backup for a OTP hack, but again afaik it would be easier to just restore a standard backup and from there continue with the OTP dump via software
As for OP, at this point you have to hardmod if you want to continue with this hack. You could either hardmod now and restore your backup you created on your SD card, or you can use safe mode to update to 11.0 and from there hardmod and downgrade to 9.2. Either way, at the time of creating this thread, a hard mod is needed for you to continue trying to install a9lh