Without iTunes, you have also another way to find your UDID of iPhone or iPad, which is to take advantage of online UDID finder website to search for UDID. The following part will show you how to find out UDID without iTunes.
Step 1. Open the browser like Safari on your iPhone, iPad, and visit udid.io (https://get.udid.io/) where you can see the "Tap to find UDID" option.
Step 2. Tap the "Tap to find UDID" option, then you will be asked to install the "Get Your UDID" plugin.
Step 3. After installing the plugin, you will get your UDID of your device in the site. Here you can also tap "Send UDID via E-mail" to export and save the UDID of your iOS device.
The profile is from Apple, so it should be safe.