The new check box 'Ignore system input language' in Tools > Options> Language Settings > Languages has no help. There exists neither an extended help text nor a section on the help page, where all the other options of this dialog page are explained.
Confirmed. What Regina means by 'help' is basically this: https://help.libreoffice.org/Common/Languages where indeed the help entry for 'Ignore system input language' is lacking.
More info: https://gerrit.libreoffice.org/gitweb?p=core.git;a=commit;h=b4d1aaa0 Description in config schema would be good as help text.
Andras Timar committed a patch related to this issue. It has been pushed to "master": http://cgit.freedesktop.org/libreoffice/help/commit/?id=b1cfd2b985bedae8929c2d798815b88e630e7a28 fdo#59209 add help text for 'Ignore system input language' The patch should be included in the daily builds available at http://dev-builds.libreoffice.org/daily/ in the next 24-48 hours. More information about daily builds can be found at: http://wiki.documentfoundation.org/Testing_Daily_Builds Affected users are encouraged to test the fix and report feedback.