How to transfer data (minus my Aperture Library) from a Mojave iMac to a new Monterey iMac ? ‘Conflicts Detected’ issue?

Dear Apple Community,

This is a bit of an Odyssey so my apologies. What with one thing or another over the past few years, I have not been able to commit myself seriously to finding a new home for a sizeable Aperture (3) Library which I currently keep on a 2017 iMac, using OS Mojave (10.14.6) and backed up with Time Machine. A couple of weeks ago, however, the ISP anti-virus software update failed the compatibility test saying that it was suitable only for OS 12 or later. So, in the meantime, I have bought a 2020 iMac which came with 2 TB SSD storage and OS Monterey installed on it. The plan is to use - temporarily - the 2017 iMac solely for my Aperture Library while I update my life! to OS Sequoia. 

Realistically, due to the ‘fragile’ state of the Aperture Library, I did not think that transferring my data from the 2017 iMac to the 2020 iMac was going to be as straightforward as any transferring I had done in the past. That said, I imagined that the 32-bit AL would be transferred over as usual but that it would be unusable in the 64 bit system from Catalina on and so I could delete it after the transfer. As in the past, I used Migration Assistant (this time via Thunderbolt) which divided the data to be transferred in to four folders: Applications, User, Other Files and Folders and System and Network. All four accompanying boxes were ticked and I saw the notice that there were ‘conflicts’ to be fixed. I was instructed to make sure that all the info I wanted transferring had been ticked and to then click on ‘Continue’ which I duly did. I was prepared to let the ‘Getting Started’ stage run for a while on the basis that it would take extra time to process the library but after about nine hours of leaving and returning intermittently to check if it had, I cancelled the process.  Is it the Aperture Library in the data being transferred that is triggering the 'Conflicts Detected' message during the Starting Up?

After cancelling, I clicked on the ‘back’ button and noticed a couple of things: i) the ticked Applications folder (1TB) was not openable; ii) the ticked User folder (345 GB) could be opened and this folder contained separate ticked folders for: Applications, Desktop (63 GB), Documents (5 GB), Downloads (11 GB), Dropbox (2 GB) but the ticked Applications folder had no accompanying GB data count.

On Thursday, I contacted the Apple Community after I had copied my Aperture Library back to its default folder; Pictures, from the Library folder in the Macintosh HD location. My question then, to which Neil responded Yes, was whether or not it would be OK to delete the AL in the Library folder. 

This morning, (Saturday), before contacting the Apple Community again, I decided to give migrating one more try. My main observation this time was how the 1TB data count for the Applications folder had dropped to 121 GB. Fair enough, I thought - the AL info calculation being 880 GB – but… I couldn’t see an equivalent increase in data in any other of the four Migration folders. I have checked and the AL is still in there, which, I suppose, begs the question? Is Migration Assistant programmed to detect the Aperture Library and to stop its transfer on to a new(er) iMac?  

After that, I came across an Apple Community response explaining how the ‘Conflicts Detected’ notification was linked to the account number and password of both computer being identical so I changed the password on the new iMac. However, ‘Conflicts Detected’ notification still persists. What's causing the Conflicts detected message?    

So, finally! What is stopping me transferring the data between the two computers? The Aperture Library?Thank you.