Just so you know, Start11 has been installed by many other users, but you're the first to report this particular issue—at least to my knowledge.
The link I shared earlier points to a different topic, but the method described there might still help in your case. Try pressing the Tab key to see if it jumps to the missing radio button. If it does, you can use the Enter key to select it. Once selected, the "Next" button should become clickable.
Also, what do you mean by this? Which public website was you referring to?
I have tried Start11v2-setup.exe (downloaded from the public website)
End of hainguyenthanh5's quote
Thanks again!
Basj,
Stardock Community Assistant