download Linux dowload assestent
cd ~/Dowloads
chmod +x UnitySetup-2018.2.7f1(here you have to put your version)
cd
~/Downloads/UnitySetup-2018.2.7f1(run the installer)

and to lanch unity, just type,
~/Dowloads/UnityS-2018.2.7f1(again you have to put your vertion here 2018.2.7f1)