Sometimes when opening a world to LAN the client will hang and require force quit when choosing "Save and Quit to Title".
This does not happen every time but rather once or twice out of 3-10 times trying it but sometimes more often.
Step to recreate:
Create new single player world all default settings.
Hit escape and click "Open to LAN"
Turn "Allow Cheats" to ON
Click "Start LAN World"
Explore the world for a few minutes
Hit Escape key and choose "Save and Quit to Title"
Repeat couple or so times until in hangs if needed
To me it acts like the network stream is not being closed every time.
NOTE: Upon force quitting the client the launcher does reappear with the Game Output tab selected but there are no errors.
Linked issues
Comments

NP. I have put your description in MC-72943
Very sorry I checked before posting this and could not find a duplicate. Sorry for wasting your time. 🙂