Think I may have found the solution to this problem. It has to do with page file system. In watching a tutorial video, it describes how to fix it. This seems to have worked for me, so far. No crashes in 1 hour of gameplay as it stands right now.
Follow along and see for yourself. The narrator may be hard to follow due to accent. You can turn down the volume and enable captioning "CC" on the video if you want.

Skip to 1:52 of the video as the first part isn't really necessary. Thanks to PCHelper for this!

Hey sir how did you get those logs showing Ubisoft connect losing connection?

Same here. I am running a 5700xt, with 32GB of DDR4 RAM. The game is installed on a 1 TB MVMe SSD drive and it just wont work for more than 20 or so minutes. It randomly dumps me back to the desktop. And on one of my crashes, it just rebooted my whole PC. I've tried so much random crap to fix this and I can't. I am ready to give up and just not play any more future Ubisoft PC releases if they aren't going to respond or at least show some sense of urgency.

@painshadow Man I tried that too, no change...

@fantazyz78 Tried this and a million other things no change for me.

@camokillo Same man. I can't get this thing to run for more than a few minutes. Tried even rolling back drivers for my 5700XT and nada...

So I was 4 hrs into this game and the problem surfaced after I finished the mission where you kill Kjotve's spies. Every time I open the map the game crashes and the screen turns black(though audio still runs).
The only way to restart is to press and hold the power button, and I have to do this several times otherwise it just freezes on windows welcome screen.
I've tried lowering the graphic settings, verifying game files, running offline and reinstall the entire game but none of these worked.
My specs are:
intel core i9-9900k
intel Z390 chipset
32g ddr4 2666mhz RAM
512g ssd
Geforce RTX 2080ti-11g
Anybody experiencing similar problems?

@ubi-litten i've formatted my pc since then, ran the game in admin mode, tried a lot of magic and for now it seems to be fine but I did not had time to play for hours yet, i'll keep you informed

I have travelled to Vinland and now every 3-5 minutes the game crashes, I spent 45 hours into this game now it just feels like a waste of time. On top of that I seem to drop down to 15 FPS quite frequently. I am on PC with a 2070 super and 16gig of ram. Please find a way to fix this.

And still Ubi dont do nothing.. iam getting angry after almost 100hours i still have sooo many game crashes

@katb0xsuicide

launcher_log.txt file. Default location is C :\Program Files (x86)\Ubisoft\Ubisoft Game Launcher\logs

I have many crashes too and am showing the same connects and disconnects of the same files, using Ubisoft+. Unplugging or disabling internet will eventually cause the game to stop working with a Ubisoft error from Ubisoft Connect stating an active online connection is required to play games using Ubisoft+. Unfortunately only one crash report was identified by Ubisoft out of the 30+ crashes I have had so without crash reports good luck on this being fixed.

I have these too... its soooo mess.... i played about 100 hours and maybe this happen 100 times sooo many crashes, bugs, lags... when i play odyssay i havent this kind of trouble...

Increasing the swap helped me. I noticed that the game crashes when my 3GB swap is 100% full. Having increased the swap up to 6GB, the dropping stopped.

Sharing for anyone with the specific issue of the game closing itself every 15 minutes. Works on any Uplay title with this problem:

First, I want to mention that I have played on my PC before. The last time was 2 days ago.

All of a sudden I can not start the game. When I do, it loads the AC greenish boot screen and then it disappears. After it disappears, I get an game UBISOFT Connect error that says, "Oh no, it crashed! Assassin's Creed Valhalla crashed. Help us out by sending a crash report so we can figure out what went wrong". I have sent the crash report twice. I also tried uninstalling and reinstalling the game as well. And then I ran a "verify files' check in the properties. After all this, I still get the error. Please help.

Thank you,
-CRASHFIRE

Can we change the button for laying an explosive trap to L3 instead of R3?
It interferes with oden sight when around enemies.
the traps blow up when any AI is around then including friendlies which ruins the trap and alerts enemies

Also would like to see more options for settings allowing players to customize their experience in Valhalla (ie marking enemies with raven option, increasing difficulty/timing of parrying, making a drengr version of stealth etc) This was done recently with the Ghost Recon breakpoint update and would be greatly appreciated in Assassins Creed Valhalla.

been playing fine for hours until yesterday, right around the time Reda's shop started to show nothing, and then when they release the new pack i believe? and after that my game would crash to desktop whenever they wanted, every so often. Quest breaking and not completing, mission not registering properly. I dont know if it's just coincide with the timing, but I somehow pretty sure it has something to do with the latest store update? But yea overall possibly due to ubisoft plus or something.

@residex9 having the exact issue. Sound is still on though.

What does the "Event Viewer" say? - Anything in the crash logs?
To me, it sounds like the graphics driver is crashing, but it could be completely different, though.

mines been doing the same since release day every 15 mins it just crashes, sometimes the game closes and sometimes it restarts my computer when it crashes.. annoying!