@ubi-borealis So...

1. I've completed all troubleshooting I could think off and everything you guys suggested, as I mentioned when I ran out of those I also googled around for possible random fixes like setting myself to offline on Connect/disabling overlays and popup messages. Nothing worked, game still crashes randomly (either in overworld or any of the menus, can't even switch gear). Event Viewer says some kernel base error is connected to my crashes.
2. I9 9900K up to 5.1ghz, 2070 Super, 16gb ram, 1 NVME SSD, 1 regular SSD and 1 HDD, a power supply and mother board to hold it all together. In case it matters, I have a soundbar jacked in via optical cable, a wireless Xbox One controller, keyboard, mouse and dual monitor setup, one is 1080p 165hz and the other is 1440p 60hz.
3. Yes, I've completed one save up to 94% game done without crashes back then, there were bugs like the festival cloak that wouldn't go away even after quest, then uninstalled after first dlc and waited for everything to be released.
4. I re-downloaded the game about a week ago as I wanted to play the Kassandra update and this time around do a 100% run. The crashes were happening right after a fresh installation.
5. Coincidentally I recently also updated from win10 to win11. I've had issues in light of that change on other software too so I wouldn't be surprised if it's linked to my problems. (Just in case it helps - similarily Star Wars The Force Unleashed Steam version wouldn't run for me no matter what after I switched to win11, event viewer also had a kernel error. So someone on steam forums linked me an update to dx9 from the Microsoft website, I installed that and the game ran near perfectly, some missing sound files here and there.)
6. No, none. The only trigger for the game crashing is that it's running and I'm not kidding, it can crash either in the loading screen, either overworld, either in menus. can't even view tutorials. I downloaded over 100gb worth of data to my SSD to watch crash messages galore. Old save, new game, doesn't matter, one thing I did notice is it doesn't have trouble parsing video files but it does have trouble as soon as anything 3D related starts. For example, one time a new game didn't crash right after the 3D render of little Eivor starts and I could get through to the part where you're then adult Eivor. First it crashed in the first adult eivor cutscene where he/she is tied on the docks, then second time I skipped it... and I crashed as soon as I walked about 20m or so. I continued and fired up the game one more time, this time I crashed at the first Viewpoint when I pressed F to focus on it. It's just impossible to get anywhere without just watching the intro messages all the time. I'm pretty much rendered being unable to play it at all. I know your intro messages by memory by now. And one time I've also just let it run without touching anything in the main menu with continue, new game etc. It also crashed on it's own after about 5min or so.

I hope this helps. If you need more, say the word.

EDIT: Even did a fresh win 11 installation (I thought that the fact I upgraded instead of freshly installed it could have messed up my files). So after that, first thing I downloaded was Firefox through Edge, then Ubisoft Connect through Firefox. I installed the game. It crashes exactly the same as it did before, no change... so I'm pretty sure this means nothing on my side is wrong and I sent you 2-3 more crash reports right after. And I've been filling up this post with more info up above as I did more tests to try to find out what's causing all this and also some more things that I've noticed about the problem.

PC version, 1.5.1 patch. My game constantly crashes at random points but so often I can't even be ingame for 1 minute. I could play the game perfectly fine before the Kassandra update but truth be told I had it uninstalled since I played the first DLC. In between I upgraded to windows 11 from windows 10. I made sure everything is okay and updated to the latest drivers and I have done all of the troubleshooting, when I ran out of that even some google solutions that did not work (setting myself to offline in Connect and unticking the overlay features). So for me it is unplayable. I cannot even switch gear or travel more than like 100m before it crashes. I will uninstall it until this is fixed, I sent you plenty plenty of crash reports over the past few days.

On 1.5.1 PC version I have constant crashes and I can't get around them. They can happen anywhere in-game, from menus to the overworld. I downloaded the game again in hopes of playing the new Kassandra story but sadly I can't even play for a minute or more. I managed to start a new game... that again starts crashing the moment you're adult eivor. It's literary unplayable. I've sent several crash reports to Ubisoft over the past few days, I really hope they can look into it... Win11 could also be a factor, I upgraded recently. I was so happy but now it's just eating that ton of space while I can't even play it Literary like a minute of playtime is all I get before it just goes adios. I sent a crash report every time...

That is indeed interesting. Did you notice any FPS difference? Any visual difference?

I just want to point out some stuff I really want to share with both devs and the community alike.

First of, the moment I fired up the game, I was introduced to this amazing looking scene, the lightning and how it played with the environment, the characters sharp well-styled aesthetics. Amazing. The intro story felt almost like a Game of Thrones story and I think as I played with the female Eivor I often thought of her character similar to Arya.

Well that aside, the combat compared to the previous games feels more real and a little less arcade which is great, but I'd hate it being any more real. This is the perfect balance now, no teleporting around with skills. Don't get me wrong, if you can asociate it with Isu technology, any kind of magic is fine - I'm in love with the Excalibur and Mjolnir combo. Every fight, the moment I lock onto an opponent starts feeling like a dark-souls boss fight, the camera changes, the ever-so-slight time-slow effects, the really nice look of particle effects. And even looking a bit further away it just feels like a proper realistic fight with diverse tactics (I play on Drengr). Now imagine having a whole wide world of fights and encounters, wars, assaults, raids, ship bow shooting or horse shooting fights and the likes - it's an amazing piece of product so far and it honestly is, noone can say otherwise, all of this is true.

There are however some problems... well there's bugs - Wolfs have hooves sounds. It feels like not all the time but they do have horse hooves sounds - I can't imagine any loud clucking sound with their paws being soft as can be. Lincolnshire was bugged for me, the follow Hunwald quest to some camp was frozen, nothing happened at the table. The last update fixed this for me and I was finally able to go past that point. I randomly like to climb mountains and I see a LOT of clipping and misplaced rocks that just show the empty nothingness through the map. some bigger several times from the playermodel, I climbed a lot of the Norway mountains when I spotted about 2-3 such holes. I think I saw a couple more in England and one in Vinland, all in all this game needs a proper once-over in that regard, there's also clipping and missing polygon faces on buildings, some of them through the story. And the last region I did in England was Glowecestrescire, which bugged my cape to stay as the festival cape. I can't disable it, I can't make it invisible, it just won't go away.

And to wrap up my thoughts - The game really is gorgeous and it deserves some shots for my PC background. Here's some screenshots I made (with the bugged cloak):

well I just wanna say that I also have this problem today - I'm adding a screenshot. I'm in the endgame mission I believe yet it still hasn't gone away. I did Glowecestrescire as the final region. I hope it gets fixed soon maybe make it as an actual equip item which we can un-equip later by hand or something. I would really, really, really like to change my look sometime soon, I'm nearing 100%... just some side stuff to wrap up after.