Backup links incase the original site gets blocked: 

Link 1:   (original, ur on this one) https://sites.google.com/view/sigma-ubg/home

Link 2: https://sites.google.com/view/sigmas-ubg-1/home

Link 3:  https://sites.google.com/view/sigmas-ugb-2/home

Link 4:  https://sites.google.com/view/sigmasubg3/home

Link 5:  https://sites.google.com/view/sigmas-ubg-4/home

Link 6: https://sites.google.com/view/unblocked-games-commonlit/home UBG Commonlit

Link 7: https://sites.google.com/view/unblocked-games-clever/home UBG Clever

Link 8: https://sites.google.com/view/unblocked-games-canvas/home UBG Canvas

Link 9: https://sites.google.com/view/sigmasubgtopmenu/home UBG Top Bar

Things that backup sites don't have:

Holiday and seasonal stuff.

Not all the games the original does.

And games get updated later then the original site.