The client size I use is 1920x1080 and the in-game resolution is as well 1920x1080. When i finish any kind of game, the client ends up being very small, being unable to do anything, but to close the client, saying yes.
I've found no solution but playing with the resolution of my screen, which is in 4k. (You know, the arrow is so small i cant even see where is it in teamfights). Playing at 4k the Client keeps the resolution of 1920x1080 when ending a game.
https://i.imgur.com/PMS5mPW.jpg (On "Skip Waiting for Stats")
https://i.imgur.com/CLQxAad.jpg (On "stats" after the game)
https://i.imgur.com/o31LeHd.jpg (Confirming if closing the client or not)
Also, when i close the client while being small, when i open it up again its resolution appears to be 1024x576 instead of the 1920x1080, so i have to change it again to 1080p.
How to reproduce it:
1) Start the client with a resolution of 1024x576 and change it to 1920x1080
2) Play a game with a 4k screen at 1920x1080 fullscreen (Changing it in-game or just having it from older games)
3) End the game
4) The client should be very small (it appears at top left of the screen)
5) Close the client (forcing it or just saying "yes" to the window)
6) Open the client and see that its resolution is 1024x576 instead of 1920x1080
(This makes an infinite loop, so you can do again step 1)
This bug can be frustrating if you have to do anything after the game (for example reporting players, or seeing its stats, or wanting to play another game) and closing the client to then opening again to play again makes it an infinite loop (unless you play with the screen resoluion, but 4k makes it harder than 1080p)