Successful reinstalls so far beyond the mandatory content:
I kind of suspect the third-party airplanes from the Marketplace, as I’ve heard of a number of vague compatibility problems in existing planes with the update, and some of those planes appear as static traffic (parked at airports). I haven’t reinstalled any non-Asobo planes yet.
Same problem, can’t start flight , gets stuck with blue bar all the way to right. MSFS is broken with this update.
Same here..
Try removing all the Marketplace content; helped for me.
That is what I am afraid of, a complete reinstall. The update broke the version I had which worked great.
After you did a reinstall, did you have to run the update again?
But you can change the /active=“true”/ to /active=“false”/ in the addon.xml? That should take less time than removing the addons and then reinstalling them.
I don’t know, can you? Does it work? Did you try it?
Techincally it should work the same way as removing, because this file basically tells the Sim which addons to load or not.
So try it and report back. 
Also backup and remove the scenery indexes folder!
Ok have reinstalled additionally, fully working:
I additionally have installed the new G1000 NXi and it’s back to freezing. Weird since that’s new and supposedly works with SU5.
This is extremely frustrating. I am not a happy camper right now. Full loading bar. Yet can’t fly… I’ve downloaded all updates in content manager. Restarted computer & sim multiple times. Nothing seems to work. I knew there would likely be some issues, but I expected to at least be able to load into a flight.
(ah nevermind I misread)
Welp, it’s back to hanging. I’ll delete some more stuff.
This one was the problem for me, removed it and started a flight without problems.
The new G1000 NXi works like a charm, tested in the Bonanza
Nice. I’ll take that back out and try the G1000 NXi again 
Still hung on the first attempt to start a flight after uninstalling the N Summer / S Winter pack and the enhanced north american airport scenery and reinstalling the G1000 NXi. However it may not be ‘taking’ fully until restarting, so let’s try restarting the sim since I had to ‘end task’ anyway:
bam loads up right away.
Yup, same here stuck on flight loading page bar @ 100%
Nothr /South Foliage pack was the problem for me. Imostalled it, and now I can load flight.
So for me it was the Finland eco region mod. Remove any vegetation mod you have - that’s the issue.
Can confirm that removing n/s summer/winter foliage and restarting MSFS seems to have resolved it.
(I’m now encountering a presumably unrelated issue that all airports are uncontrolled. :D)