Issue seems to be solved now. I changed the graphics from nvidia-510 to nvidia-470 in Software and Updates.

I removed earlier installs:

sudo apt remove steam steam-launcher steam-installer

sudo apt purge steam steam-launcher steam-installer



sudo rm -rf ~/.local/share/steam

sudo rm -rf ~/.steam

sudo rm ~/.steampath

sudo rm ~/.steamid

sudo rm -rf Steam

sudo rm -rf /usr/lib/steam

Then installed steam via wget

sudo dpkg --add-architecture i386



sudo apt update

sudo apt install wget gdebi-core libgl1-mesa-glx:i386



wget -O ~/steam.deb http://media.steampowered.com/client/installer/steam.deb



sudo gdebi ~/steam.deb

Then ran steam via terminal

steam

This solved my problem!

P.S.

Also, when I ran steam through terminal, an error was shown:

Could not connect to X session manager: None of the authentication
protocols specified are supported

For this, a solution was mentioned on the steam website to check $DISPLAY

echo $DISPLAY

DISPLAY=:0 steam

Don't have much idea what this is (I AM NEW to Ubuntu and anything open-source). This might help if nothing above this helps.