UASP support on an iMac - Late 2015

You bought the base model iMac with 8 GB of RAM and a glacially slow 5400 RPM HD. These machine were designed to be e-mail and minor web surfing machines and not too much else. Your computer appears to be operating correctly for it's specifications from what I can see on the report. The only thing that can be done to improve performance on this machine is to buy a USB 3 external SSD and then clone the internal HD to the SSD and use the SSD as your boot drive. The drive I would recommend is the:

https://eshop.macsales.com/item/OWC/MS8U3SSDT1.0/ with a

https://eshop.macsales.com/item/OWC/MOTGPWR/

This upgrade will improve performance substantially.

The other thing I noticed is this computer has no backup plan which is a 100% guarantee of lost data. At the very least you should be using Time Machine to backup the computer. What experienced users on these forums use are OWC Mercury Elite Pro as they are reasonably priced, dead reliable and can be easily maintained and the vendor provides excellent support. If you are not familiar with Time Machine please refer to Back up your Mac with Time Machine

That article is from 2015 which means it is almost 6 years old. And, I have no idea if that outdated technology would work or not. There is a much better way.

I will assume that you have the default super slow 5400 rpm spinning drive - they do everything extremely slow. To make sure, please download Etrecheck, run it and post the result here using the third little button in the toolbar (additional text). If your main problem is the slow drive, you can do this (right now just an outline):

www.etrecheck.com

Get an external SSD in an enclosure, plug it in, format it for Mac, download CarbonCopyCloner, create a bootable clone on your external and then simply use it to boot and work from. You do not need any other software.

I said that the article is several years old - and, in electronics, 6 years makes anything outdated. But, to be fair, I am not familiar with their products. SCSI is a very outdated technology - they claim it is now fast. I don't know if it is or not.

And, it does not mention anything about being bootable. If you want to boot from an external drive to make things work faster, then you better check into that.

The only way I can recommend is to get an external SSD, format it for Mac, put a clone of your system on it and use that as your startup disk.

And, according to the report, you do have the super slow 5400 rpm drive. You also only have 8 GB of RAM which is considered the absolute minimum for the latest OS, but there is nothing you can do about that. So, an SSD would speed up things considerably, but, depending on what your workflow is, the RAM may still be a (smaller) problem.

Additionally, icloud is basically a syncing mechanism - it makes all your stuff available to be looked at/worked with on all of your devices. However: if you delete something off your iMac, it'll disappear in icloud.

So, yes, aside from the fact that I would not trust my personal info to an anonymous online server, do get one or two external hard drives (no need to spend money on an SSD for a backup as it'll run in the background) and make regular Time machine backups. I like clones because they are bootable, so I have those. At the moment, the only one working with Big Sur is CarbonCopyCloner - read up on it at bombich.com. It will make a clone but, because of Apple's lockdown of the OS, it cannot directly clone the OS itself: you create a clone and then install Big Sur onto it which makes it bootable (I just tested that and it works).

You are mistaken about iCloud, it is not a backup plan it is a storage plan. Time Machine or a bootable clone solution is a backup plan. I urge you to begin using that. iCloud does not backup Mac OS or your settings and likely not your apps either. Please begin using a proper backup solution, at a bare minimum Time Machine.