Streamlined Migration of FRS to DFSR SYSVOL

Hi.

I'm in big trouble.

I only have one 2008 R2 DC on this domain (domain level 2008), and, I am needing to migrate FRS to DFSR as I need to join a 2019 server to the same domain and then demote the old one.
However, I'm stuck at:
"Unable to create DFSR Migration log file. Error 5 The following Domain Controllers are not in sync with Global state ('Prepared'):
Domain Controller (Local Migration State) - DC Type
2008CSERVER ('Start') - Primary DC
Migration has not yet reached a consistent state on all Domain Controllers. State information might be stale due to AD latency."
There's enough free disk, the correct security policy for the built-in admins group is set, the AD Replication Tool shows no errors at all, nothing (not that there are any other DCs to replicate to anyway), and, Dcdiag /e /test:sysvolcheck /test:advertising is successful. (I went through all the steps in this article)

I then did Dfsrmig /setglobalstate 1 but it's been three days now and I still get the error above.
Any thoughts?
A sysvol DFSR folder has already created inside the windows/sysvol folder, shall I just try the nuclear option of Dfsrmig /setglobalstate 3 ?

(I later tried that, and, while I was now able to join my 2019 server to the domain because FRS was eliminated, my "nuclear" option is stuck at the following state: The following Domain Controllers are not in sync with Global state ('Eliminated'):
Domain Controller (Local Migration State) - DC Type
2008CSERVER ('Start') - Writable DC Migration has not yet reached a consistent state on all Domain Controllers. State information might be stale due to AD latency.)

Do I just do /deletenotntfrsmember now? Also, how do I test that this has worked, I mean, on my new DC, I've already transferred all FSMO roles to it and I can access AD and GPMC and so on but the sysvol folder is empty... Can I just manually copy everything from sysvol from the old DC (since there is only one) and then run /deletenotntfrsmember ? (that server is going to be decommissioned anyway)

I have a sysvol DFSR folder on the first (old) server now, and it's got all the policies in it, however, nothing replicating over to my new 2019 DC which has a sysvol folder. (it's just empty)
So do I just manually copy stuff into it, or, what do I do?

I think this article is missing a step about checking something, as, I checked everything and it was all fine yet I was still stuck. This was all before the 2019 server was promoted to being a DC.

I am decommissioning the old DC anyway, and, will have a new secondary 2019 DC that I haven't even set up yet. If I just copy stuff manually into the empty DFSR folder on the current new 2019 server, and then decommission the 2008 r2 one, will it then just work with a new secondary 2019 server?

(I've already transferred all the fsmo roles to the new 2019 DC, do I have to transfer them back to the old one so as to be able to fix this?

I checked on the 2019 DC, and, while I have now manually copied files over into the sysvol folder, it is not even shared on the network, if I do a \\2019dcserverhostname, there are no shares that appear at all, which is weird.)