In Calc, if a word has an apostrophe (') within it, it seems like you are unable to add it to dictionary. After right-clicking it and selecting "Add to Dictionary", the red squiggly line still persists. I tried adding the same word to LibreOffice Writer, adding it dictionary, and it worked. After launching Calc again, the word no longer has the squiggly line. This seems like a problem exclusive to Calc.
Thank you for the report. Reproduced in: Version: 24.8.0.0.alpha1+ (X86_64) / LibreOffice Community Build ID: 5a75414d1772d1fd998f405e3b9bd80b1f10c51f CPU threads: 8; OS: Linux 6.5; UI render: default; VCL: gtk3 Locale: en-AU (en_AU.UTF-8); UI: en-US Calc: CL threaded Also the case in Draw and Impress. Let's make as duplicate of bug 150582. *** This bug has been marked as a duplicate of bug 150582 ***