The usage of array formulas in LibreOffice (with a result needing more tthan one cell for the output) requires to lock a fix output range. This reduces its value/usability in cases where a variable size of the output range would be preferrable (like in the UNIQUE-case), and aggravates the maintenance of the sheet (insertion/deletion of rows/columns e.g.). Have Google (their “-Sheets”) means to solve this conceptual problem or do they simply not worry and leave it to the user?
Calc hasn’t a UNIQUE function, but if the mentioned issue isn’t relevant for a user, its not difficult To create a sufficiently efficient implementation of it even with Basic code, as long as not the sheet is misused to mimic a database, and has many thosands of data sets.
Personally I use a combination of TEXTJOIN() combined with a user function XTEXTSPLIT() for textual cases of the task, but restrict this to a few dozen rows in usage. XTEXTSPLIT() comes with UNIQUE by mode parameter.