external bootable media is not showing up

If the supposedly-bootable USB device is not showing up and you're following the Acronis docs and if you're running the latest version of the Acronis software, then there's a problem with the MacBook Pro hardware, or with the USB device you're trying to boot, or with the USB supposedly-bootable device software contents; with the Acronis software or instructions or with the installation of the Acronis tools.

If you're not running the latest version of the Acronis software on the supposedly-bootable device, start there. Download the Acronis software and generate a new USB device with the latest available software, per the vendor docs, and see if that works.

For testing, remove all externally-connected devices, all hubs, all Thunderbolt devices, all FireWire devices if your particular MacBook Pro has that, all Mini Display Port, everything. Everything except a USB keyboard and mouse if you're using those—and given this is a MacBook Pro, you shouldn't need to have an external keyboard nor mouse connected (just) for testing.

To differentiate a potential hardware problem here, create a bootable macOS installer, and see if that works. If that works, then your Mac hardware and the particular USB device used are capable of booting.

If that does not work, then there's a problem with the Mac USB hardware or with the USB device. Try a different USB device, and preferably from a completely different vendor and different batch of devices. And again and just for testing, configure no other external USB devices, nor USB hubs, nor any USB cabling connected. Strip the USB configuration to the minimum hardware.

If the MacBook Pro USB hardware still isn't working and isn't seeing and booting the macOS bootable installer and you've minimized your externally-connected-hardware configuration, then check with Apple Support or the local Apple Store, or with your preferred Apple repair provider.

If the hardware is able to boot and access the macOS bootable media you've just created, and if the Acronis software is the part here that is seemingly not working, not recognized or not compatible with your particular MacBook Pro, check with the folks at Acronis support.

There are also some discussions of some potentially-similar issues over at Acronis, too.

If you're wanting to make a clone, why not use "tried and true" or "proven to work with mac" software such as CCC or SD? I've been working with Macs for 25 years and had never heard of the software you are using/trying to use. CCC in particular does macs and does it well. Any software that is for all OS versions or was at first developed to work with another platform and then "adapted" for Mac OS, may not be truly compatible.

If the USB drive shows up when plugged in, but you can't boot from it, then that means that something did not go right and you do not have a bootable drive.

So, without some very detailed info (more than "a backup and recovery software that i have") on how, using what software, etc this was created, it is impossible to guess.

Whatever backup approach you might choose, test the recovery from bare hardware.

i’ve chased more than a few add-on backup tools for enterprise computing sites, and with decidedly mixed results. Some of these mixed results involved very well-known vendors, and sometimes even the system vendor’s own add-on tools, too.

Here, dd and Disk.Utility can capture a whole storage device. Or as can add-on tools, though—if the third-party package you’re using isn’t working—check with the folks supporting it. And again, test the bare-metal recovery ahead of when it’s needed.

Untested backups can be better than no backups, but—having encountered bad backups, bad media, bad hardware and bad backup software in multiple cases—can also be more time and effort than simply not bothering with backups at all, for the same end results: data loss.

The other reason to occasionally test backups is being able to experience and document the recovery sequence, and without the added stress and time-constraints that often arise during a failure, damage, theft, loss or other outage.

Testing macOS will require another Mac, if you’re not willing to wipe the current environment. And if you’re not eilling to do that wipe-and-test, are you really trusting your backups?

I think you really need to speak with Acronis support. If they claim one can boot from Acronis True Image they should know the ins and outs on how to accomplish it.

I am not familiar with either, so we'll need to wait for someone else to pop in; but, as for the linux, I have no clue how you could produce a bootable Mac OS drive using a different OS.

And, you said you downloaded a boot media iso - not sure how that works either. FWIW, the only legal way to obtain Mac OS is to download it from the app store (Apple).

Here are the usual recommendations for creating bootable media:

https://support.apple.com/en-us/HT201372

As for myself, I prefer to use bootable clones using CarbonCopyCloner or SuperDuper.