Android 7のWiFiデバイス名を変更する方法 -- settings フィールド と 7.0-nougat フィールド と device-name フィールド android 関連 問題

How can I change the device name of an unrooted Android 7.0-based Gigaset GS170 smartphone so it appears with a meaningful/readable name e.g. in a router's list of connected wifi devices?

Various resources (e.g. this or this) suggest I should find a line saying Device Name in the About Phone section of the phone settings. However, I can see no such line there (images before and after scrolling down):

As the device is set to German, here are the translations of the items in their order of appearance:

• System Updates
• Status (Phone number, signal, etc.)
• Legal notes
• Model type number
• Android version
• State of security updates
• Baseband version
• Kernel version
• Build number
• Adapt creation version

Is there somewhere else I could look for that option, or is it something only supported by specific devices?

There are a few questions about this on this site (e.g. this and this), but those were posted several years ago, when early versions of Android with some "childhood diseases" (read: lack of basic features) were still the state of the art.

AFAIK it's possible that a phone manufacturer hide that option from UI on their products, and I guess your phone it's one of them. My phone OnePlus 5, however, does allow changing it from Settings app.

So, if root access is available, try this in a rooted terminal environment:

setprop net.hostname "Whatever You Like" 

Mount /system partition as R/W, head for /system/build.prop. Find this line and if it exists, change it (this line may not be present on Android 5 or lower):

ro.display.series=Same As Above 

Reboot is required. After that the new name should have effect. Before modifying build.prop consider making a backup of it (and have a means of restore, e.g. via recovery-mode): if the file is "broken", your device won't boot up properly.

On my Android 7 phone (Zenfone 3) I was able to change the bluetooth name as follows:

1. Open "Settings"
2. Open "Bluetooth"
3. Select the action bar (the three dots in a vertical line in the top right of the display)
4. Select "Rename this device"
5. Enter the desired device name for bluetooth purposes
6. Select "Rename"