Having the exact same issue on Windows 10 (I'm not sure if using windows has a correlation with the issue but putting that out there just incase). Loads to 100%, then the screen freezes. CTRL+ALT+DEL into task manager opens the task manager but that doesn't accomplish much since I can't tab out of the game to force close it. The only way to get back into game is to restart my pc and by the time I start the game I'm already a couple minutes behind everyone else and get blamed by my team for something that I have no control over. This has happened sever times throughout all game modes, draft, TFT, urf, aram, everything. One thing to note is that it doesn't happen all the time but once it happens 1 time, it tends to happen a couple more time following the 1st incident and then it randomly stops again and the issue comes back later and the cycle continues.
I never post anything on these discussion boards about any issues (or anything on the internet in general) since most of them are minor and I just kind of deal with them even though they are super irritating, but this issue is too major to not say anything about. It's really dum that I get put into deficit that I have to endure for the rest of the game because of how punishing the game is and have to deal with the inevitable flame when we lose and it's all my fault. And I agree it is because of me we lose since I wasn't there from the beginning, but it's not under my control.
Sorry this is so lengthy, I'm just frustrated with this issue just like everyone else on this discussion board. I just want to know if this is something that's being looked at and worked on. Thanks riot incase someone is already working on this, I just wanna play the game and get a fair shot at winning.
PS. is this what it feels like to be a keyboard warrior?