Deactivate the following option:
Tools > AutoCorrect Options... > Options > Capitalize first letter of every sentence
It seems that it doesn't typically trigger (i.e., I can put a cell that contains
table, or another one that contains
this is a message and nothing autocorrects). But under certain circumstances, it is indeed triggered (e.g. when you put
t is capitalized). I am not sure why LibreOffice decides that having a hyphen means that it is a sentence and thus should be triggered.
It seems a misbehaviour of LibreOffice, or a bad heuristic. I am not sure if that's your specific case, but for sure it is what was happening to me, @dennisjbell and @AlphaCentauri.
@m93a comments may be relevant: If you are using LibreOffice version >=7, menus may be moved, and you can access the traditional ones by
⚙️>User Interface and change to Standard Toolbar
And change back by: