Hi KoroKara thank you for taking the time to report this bug!
Please let us know if Orion opens normally on 1.5.6 (3)?
Also, would you be able to share the crash report on your device? In your iPhone, open Settings.app and navigate to: Privacy & Security → Analytics & Improvements → Analytics Data, open the most recent entry starting with "Orion" and share it with the share button. If there's no "Orion" entry from the time of the crash, look for one starting with "JetsamEvent" instead, iOS creates that one when it closes an app for using too much memory. If you don't feel like sharing on the forum, you can send it to me directly at jet [at] kagi.com.
Thank you for your help in making Orion a better browser!