Switched ISPs to Frontier yesterday, had no issues until this morning. My phone is Android, my wife has an iPhone 12, mine keeps dropping Wi-Fi, hers will not connect at all. I have to forget network and re-enter my password on my phone every time I use it in the house. My wife can't even do that, it simply does not connect. We have a brand new Sony TV that worked fine last night. Today it will not connect at all. Had to switch to an older mesh router system tonight to get anything to work, the speeds are 1/10th of what I'm paying for. 

I've seen people say this is a problem with Apple devices, I assure you it is not limited to Apple.