@jlfranklin mentioned Database SSL Check in https://github.com/backdrop/backdrop-issues/issues/4772#issuecomment-778.... That is a D7/D8 module, and it could of course be ported to Backdrop contrib, but it's only a ~40-line implementation of hook_requirements(): https://git.drupalcode.org/project/database_ssl_check/-/blob/7.x-1.x/dat... ...so I believe that it could be a nice addition to core, as part of #3624.
I've installed the module in Backdrop (simply modifying it's .info file), and this is what it adds:

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There is a Drupal 7 contrib module that "lets the administrator see all administration pages in her preferred language" and which could be ported to Backdrop: https://www.drupal.org/project/...
Allow admin to select admin language seperate from front end language (multilingual)
@stpaultim – You're right: my approach affects also the main menu. I guess, because menus are also considered as user interface (not as content). @findlabnet – If I didn't miss anything,...
Allow admin to select admin language seperate from front end language (multilingual)
Go to the account edit of the desired user. On the horizontal tab below "Region and Language," select "English" or another language. WFM.
Allow admin to select admin language seperate from front end language (multilingual)