"Accept-Language" header sent by Chrome browser on Android What exactly it depends upon?

For example, if I have only one language specified in the Settings, but the Accept-Language header appears as:


  uk-UA,uk;q=0.8,ru;q=0.6,en-US;q=0.4,en;q=0.2


How can I remove extra languages?
As far as I tested, the following behaviours apply to both Android and Linux Desktop versions of Google Chrome:

Every time you change your system locale (via LANG environment variable on Linux; or via System - Languages settings on Android), Google Chrome resets its own language settings (and the Accept-Language header) to a pre-defined list. 

For example, if you set system locale to "English (Canada) / en_CA.UTF-8" and restart Chrome, the Accept-Language header will contain four locales: en_CA, en_GB, en_US, and en.

In Chrome settings, you can adjust the list of languages, leaving only "English" (no region suffix), and after a restart of Chrome, the Accept-Language header will contain only one locale: en.

I do not know about uk / ru languages, but you could try adjusting the language list in Chrome settings (don't forget to restart Chrome) and visit https://httpbin.org/headers to examine your Accept-Language header.