I requested standover heights from Orbea earlier this season when I was trying to determine whether to test ride one. This was their response:

"The 53cm dama series in any bike is going to be the same as the regular
bike in the next size down. So Onix Dama 53 and Onix 51 both have a
29.3 stand over. The next size down is Dama 51 or 48 reg is 28.4."