How to wirelessly mirror a MacBook onto a smart tv without Apple TV?
After I did upgrade to Catalina, I can use AirPlay button in the menu bar. 



The only requirement is that TV and MBP are on the same network. Picture quality on Macbook will be lower than on TV actually.
Tested with MBP Late 2016 (10.15.3) and LG 43um7500pla (4K TV).