Draw a sudoku board using line drawing characters
Python 3, 232 bytes

Thanks to those who helped to golf this down.

Encryption within encryption...



q=lambda x,y:x+y+x+y+x
r=lambda a,b,c,d,e:a+q(q(b*3,c),d)+e+"\n"
print(((r(*"╔═╤╦╗")+q(q("║ %d │ %d │ %d "*3+"║\n",r(*"╟─┼╫╢")),r(*"╠═╪╬╣"))+r(*"╚═╧╩╝"))%eval(input())).replace(*"0 "))


Try it online!

To be golfed.