After waiting for 15.1 and my several beta testers in my fleet to not report any problems, we released Sequoia to our org. About 40 users in and one of the folks running a 14" 2021 Macbook Pro who upgraded from 14.7.1 to 15.1 immediately reported that his Chrome and 3 other Chromium browsers all behaved the same way. NO pages would load. Error was ERR_CONNECTION_RESET
We tried dumping and reinstalling Chrome, running the reset command, dumping cache, turning off firewall, confirming that Safari and Firefox worked without a hitch, booting into safe mode, we EVEN went to recovery console and reinstalled the OS. Nothing helped. Apple support had suggested wiping the device entirely OR just creating a new user. Well. the new user solved the problem! So something about the upgrade to 15.1 caused something bad to happen with the original user profile. We're waiting for Apple to tell us more about 1) WHAT caused it and 2) whether there's a command to execute that can fix that user.
Regrettably neither of the 2 agents I spoke with had a familiarity with this issue (so much for the forums making their way into Apple's awareness) but they were very pleasant and professional at least :)
I suspect that people don't want to create a new user, though for some it might be a relatively painless solution.
I will update this post if I learn anything useful w/r to fixing -- or better yet avoiding -- this problem from happening.