Yes, using the Publish feature from the current Xojo release under Tahoe will generate some errors, for example the one shown in the screenshot below.
That happens because Xcode 26 did change the way their tools work in order to retrieve data from App Store Connect (for example, new mandatory options; changes in the returned format of the JSON data, etc).
We are working on that (among other many things) for the next release. Meanwhile, and as a workaround, you can use Transporter to send the .pkg file created by Xojo.
Sorry for the inconvenience 
