Slow Windows 10 Pro boot version 1903

Yes, I do remember the tests we went through, the only 2 things I don't think you have done yet are to test the SSD on a second machine (and to be honest I don't think the SSD is the issue either), and creating a new user profile, setting as default and seeing if the boot time is quicker.
As you have tried most tests and there was no difference in boot time, other than a new user profile or a clean install of Windows (deleting all existing partitions on the boot disk) with only that drive connected, I can't see us getting anywhere else with your issue.
A sideways thought here, have you tried booting without any network (so no ethernet plugged in and no wireless, easiest way is to switch off router) to see if maybe Windows is trying to find a network resource and failing, which could cause a lengthier than normal boot.

I am by no means saying you ought to clean install, I just mention it as a final resort if you really can't live with such a slow boot, it's the last resort of the desperate.
As far as what is happening in-between BIOS and Desktop, the boot log we made earlier in testing shows the loading (or attempts to load) system drivers, there were no significant errors in your boot log, the system is at this point reading from the registry and the user profile, setting environmental variables and many other tasks related to preparing to show the users desktop.
The slow boot is what initially made me think (and to some extent I still do) that the issue could be a badly behaving driver (not responding when called), app or user profile corruption.
It could well be registry corruption as well since drivers, registry and user profile are all accessed during the period between BIOS and finally showing login screen/ desktop.
The idea behind a new user profile and setting it to default to test is that if it is user profile corruption a new profile should result in a faster boot. If it doesn't then it points to a driver/ service causing problems (a safe mode boot should eliminate driver/ service issues).
You have pretty much ruled out faulty hardware so it can only really be down to the software side.
Something you could do is to use Macrium Free or similar app, take an image of your drive, create a Macrium USB or DVD boot disk then (after testing you can access the image), wipe the drive and clean install Windows and nothing else to see if the boot is still slow. If it is you can just restore the image and you loose nothing but time.
If with a clean install the boot is faster then you need to make a choice of whether to keep the clean install and add back your software/ drivers etc until you hit the one thing that causes the issue or to just restore your fully customised image and put up with the slow boot.
It is not easy to diagnose someone's machine from afar, it comes down to some basic trouble shooting (testing disks, using SFC and DISM), the rest comes from personal experience and thinking "what would I do if it was my machine". Beyond that there are just so many variables, you are the only person who knows what software you have installed, whether you are using cracked software (not accusing you, just saying I wouldn't know), if you are using customised drivers etc.
How far you are prepared to go to find the cause of the issue is entirely down to you. The options I have given you are the things I would try if it was my machine based on my experience.

Testing, tweaking, poking, prodding, analysing ....


A week has passed ... how much simpler would it have been to whip out the existing drive, snap in a new drive, install Win 10 and test?

Running faster - then it must've been a corrupt OS, and/or other offending software.
Not running any faster - hardware problem, technical intervention required.