@ovasileva Here are my initial findings on the usage of language settings. Let me know if this helps answer the team's questions or you need any additional info/breakdowns.

Note: Data below reflects events logged in the UniversalLanguageSelector schema from January through February 2021.

What is the frequency of usage of the language settings cog?

• The language settings cog is used an average 1.7 times per logged-in user that clicked the language cog at least once during the reviewed time period.
• Across all wiki projects, an average of about 574 distinct logged-in users per day click the language settings cog. For logged-out users, an average of 17,944 distinct logged out sessions per day include a click the language settings cog.
• When accessing the language settings, 71.5% [29,578 distinct users] of logged-in users used the cog in the sidebar. 33.5% of logged-in users opened the language settings using the uls trigger in personal tools and only 0.75% used the link in Special:Preference language selection.
• The majority (95.6% [1,087,759 logged-out sessions]) of all logged-out sessions opened the language settings using the cog. The remaining 4.4% of logged-out sessions opened language settings using the uls trigger in personal tools.

Distinct Users that Opened Language Settings by Method (Jan-Feb 2021)

What is the frequency of usage of any of the options provided after selecting the cog?

• After selecting the language settings cog, 46% of all logged-in users changed the display language at least once. 10.2% of logged-in users changed the input language and only 0.77% changed the font.
• Only 4.37% of logged-out sessions include a change to the input language and 0.22% to the font. Display setting changes are only available for logged-in users.

Compare the above with switching languages using the interlanguage links
Note: Data on the interlangauge usage comes from wmf.interlaguage_navigation. This schema does not include per user or per session basis but we can compare number of events to help get an idea of how frequently each is used during a similar time period.

• The number of recorded language switching events (for example, coming from de.wikipedia.org and going to ro.wikipedia.org) far exceeds (over 11 times higher) than the number of clicks to open the language settings cog in the sidebar.
• There is an average of 276,980 language switches per day across all wiki projects, while there is an average of only 23,801 clicks to the language setting cog per day.

Please see the report for further details.

All done, thank you @MNeisler!