I have ios 13.6 for a first gen SE, I only want ios 14

you can only upgrade to the latest signed version for that model which is

Current: iOS 15.7.3, released January 23, 2023[5]

iPhone SE (1st generation) - Wikipedia

you do that by reading this

Update your iPhone or iPad - Apple Support

If you decide to update your SE 1st gen, you'll get the latest (supported) iOS version for that iPhone model, now 15.7.3.

These are the instructions:--> Update your iPhone, iPad, or iPod touch

Specifically:

Assuming you're trying to update your device wirelessly, and bearing in mind that to perform such a procedure you need to connect your device to a reliable and fast Wifi Network with Internet access (no cellular data, unless you use a 5G network, no personal hotspot on your device, no VPN connections are admitted, no Low Power Mode enabled, and I suggest that you keep the device plugged into power during the whole update process), read this support article:--> If your iPhone, iPad or iPod touch won’t update (if you don't have a reliable and fast wifi network, "borrow" one from your relatives/friends/neighbors).

Also, make sure your device is NOT running a Beta operating system version. Should be this case, you need to remove it before installing any official iOS/iPadOS releases, as per these instructions:--> How to uninstall iOS or iPadOS beta software - Apple Support.

DO NOT forget to create a full backup of your device before updating its operating system, and keep in mind that, depending on the available storage on your device and/or on your wifi network speed, it might take 30-60 minutes to complete the entire update process.

If the issue persists or if the iOS version currently running on your device is very old (from your product list, it seems that the device is still running the prehistoric iOS 13), try to update it via computer (if you don't have a computer borrow one from your friends/neighbors, or ask for help at an Apple Store or Authorized Service Provider), then learn how to update your device manually if you're using a Mac with macOS Catalina or later, or if you're using a Mac with macOS Mojave or earlier or a Windows PC.

If you still get no help, contact Apple Support directly, using this link:--> Get Support

Regards

Giulio

That version is not supported any longer. By Updating, you always get the latest supported one, which obviously contain all things included in version 14, and many more.

Regards

Giulio