I believe the information is incorrect in the link. You probably need at least EPiServer.Cms 12.10.0. Try updating to latest version.
Updated it to version 12.10.0, that's not working. Linkitem property is still same textbox.
That was just a guess on my side, it was actually released in 12.11.0, https://world.optimizely.com/documentation/Release-Notes/ReleaseNote/?releaseNoteId=CMS-22342. But why not upgrade to latest, which is 12.12.0 as of time of writing this.
Thank you for all the help Johan.
Now content tree of main website is not loading after updating CMS. But LinkItem issue got fixed.
We are using EPiServer.Labs.LinkItem package for single link property in our CMS 11.20 project and now we upgraded project to 12.9. According to this link this package is deprecated in EPiServer CMS 12.6 and part of CMS. We did changes as per that link and ran script mentioned. That doesn’t make that field link item in CMS.
Can you please help to resolve the issue with this.