[General Questions and Answers] Luxon:
Found solution myself. For those wanting to have Google to translate words for you, when tapping a word on the page, here's the recipe. Even if the target language is the same as the default UI language configured on the phone, this solution will work for you.

Consider your phone's UI is set to Polski (Polish) and you want Google to translate words in articles written in Polish language into English. Because Polish is not your mother tongue.

The procedure to force Chrome translate from Polish into English having UI set to Polish consists of several major steps:

Step 1. Setting phone's system UI language to the target translation language. That's the language into what you want Google to translate your web articles. This language will show on the right side of Google translation widget showing when you tap a word on a web page.

Step 2. Specifying Chrome translation settings. Within Language settings in Google Chrome we have to configure Chrome to suggest translations for all the chosen languages. When a you read a page in one of these languages, you will be able to translate words you tap into English.

Step 3. Switch phone's system UI language back to the preferred language (that's the language that you want Google to use for system UI *and* the news.

Here are the details.

Step 1. Setting phone's system UI language to the target translation language. In this example we want English be our target language.

1. Swipe down, and then swipe again to unhide Android system settings cogwheel.

2. Tap the cogwheel. System settings screen opens.

3. In the search field atop the screen type 'language' (without quotes) in the current phone's system UI language, and then tap Języku i metody wprowadzania (Languages & input) since we're in Polish).

4. On the Języku i metody wprowadzania (Languages & input) screen tap Języki (Languages).

5. On the Języki (Languages) screen tap Dodaj język (Add language), and then on the next screen add English (United States).

6. When back on the Języki (Languages) screen tap on the English (United States) and then move English to the top of the languages list.

7. Phone's system UI switches to English.

Tip: You can add more languages here to make them immediately available in the list of target languages within Chrome language settings.

Step 2. Configure Chrome language settings to suggest translation in the translation

1. Open Google Chrome, and then select Settings in the browser settings. List of browser settings opens.

2. Tap Languages. List of search languages opens.

3. Tap the three dots next to Polish, and then tap Suggest translation. Repeat this for every language which you want Chrome to translate into English.

The key here: since we have English as our default UI language, we can specify that we want Chrome to translate from Polish. When we switch system UI language back to Polski (Polish), Chrome remembers this setting and allows us to translate from Polish even though system settings are in Polish. This is very helpful for learning languages as you always have Google Translate at hand.

4. In Chrome, open some article in Polish language, and then tap a word. Context page shows up at the bottom.

5. Slide the pane all the way up until Google Translate widget shows.

Voilà, we have Google automatically detecting source language as Polish and suggesting English as a default translation target. Now time to fix that for Polish UI.

Step 3. Switch phone's system UI language back to the preferred language (Polish in our case).

1. Swipe down, and then swipe again to unhide Android system settings cogwheel.

2. Tap the cogwheel. System settings screen opens.

3. In the search field atop the screen type 'language' (without quotes) in the current phone's system UI language, and then tap Languages & input since we're in English and want to back to Polski.

4. On the Languages & input screen tap Languages.

5. [optional] On the Languages screen tap Add language, and then on the next screen add Polish (Poland).

6. When back on the Languages screen tap on the Polish (Polish) and then move Polish to the top of the languages list.

7. Phone's system UI switches to Polish.

Done. Now your system language is in Polish, and Chrome remembers settings configured for English. You can open some article in Polish in Chrome, tap a word, and get translation into English in the Google Translate widget. To reveal the widget, slide the context pane up from the bottom of the page so the way until the widget shows up in the pane. Context pane pops up at the bottom of the page when you tap a word on this page.