I have multiple network adapters in my system and unticking IPV6 on all of them and rebooting didn’t make any change for me (Win 10).
I was able to fix it by disabling IPV6 in the Registry by following the article below, and then rebooting. Gone from 25 minutes plus to 1 minute all up.
Thanks for all the tips above guys 
I also just did a quick test and the result is … yes, it seems very plausible that a proper clock sync will speed up (enable) launching FS2024.
More details are here:
Just in case you didn’t see the other posts above, you shouldn’t need to disable IPv6. Just need to sync your time. That fixed it for me as well.
Honestly, once it worked last night I just left it alone
But I have just tried with IPV6 Re-enabled and the time sync done, and can confirm this also fixes it. If it stays in sync then I will leave IPV6 enabled. If it gets out of sync again I will probably go back and disable IPV6 again so it stays “fixed”.
Today I could finally, after weeks of trying, fix this slow loading problem on my system.
08:50 min loading time (twice as long as my MSFS2020 installation)
About 5 minutes hang at 6% “Loading Language”
In addition to that multiple CTDs. At the end of the loading process but never in flight.
I tried all the tips mentioned above, but nothing helped.
The solution was something totally different.
For MSFS 2020 I always had the framerate limited to 30 FPS via the NVIDIA Control Panel – 3D Settings. Never experienced a problem so I carried this setting over to MSFS 2024.
Seems that this this affected the framerate during the loading process and therefore the loading time.
30 FPS is 25% of my monitors refresh rate, which is set to 120 FPS. After disabling this, my loading time is 4 times faster, about 02:20 minutes!
I’m happy for now, except for this ridiculous large UI fonts in 4K and the occasional CTDs but those are other topics.
Right now in New York City 12/24/24 1:25 PM I can not get on MSFS 2020 or MSFS 2024. Just a black screen for over 2 hours. Anyone know what is going on?
**** Solved **** FS2024 stuck at 6% loading. Long story short, I installed it on another drive. Once I installed it on my C drive, works like a champ. Only takes 2 min to start it up now.