LineageOS was working great for me on my Oneplus 3T for about 6 months, but something has gone wrong with recent updates. It has started slowing down to the point of being unusable and I have to reset my phone several times a day. There have been about 6 updates since I started seeing the issue and it hasn't been addressed.

I loathe going back to Oneplus's stock ROM as they modified it to kill background processes to make the phone seem like it has better battery life. I own a Tesla Model 3 and it uses the phone as a key, and the stock ROM doesn't work well with it at all.