I’m running Kubuntu 22.04, LibreOffice 7.3.7.2. After a recent update to that version of LO the dictionaries no longer work.
I know the spell check is not working for when it is invoked:

Text language is blank. Intentional misspelled words are not flagged with red squiggly underlines.
There is an icon that is supposed to appear to the left of installed languages in this screenshot:
Said icon is absent from English (Canada) and French (Canada).
I have encountered this issue after previous updates and rectified it by simply downloading extension files (*.oxt) and reinstalling. Having downloaded dict-en-20260501.oxt and double-clicked on it, the result is best explained by the following screenshot:
The path of the file I clicked on is /home/daniel/Downloads/dict-en-20260501.oxt.
I do not understand where the system is getting /home/daniel/.config/libreoffice/4/user/uno_packages/cache/uno_packages/lu132109gxx6t.tmp_/dict-en-20190101.oxt.
Opening that directory in Dolphin it only exists up to /home/daniel/.config/libreoffice/4/user/uno_packages/cache/uno_packages/.
I tried creating /home/daniel/.config/libreoffice/4/user/uno_packages/cache/uno_packages/lu132109gxx6t.tmp_ and copied dict-en-20260501.oxt to that directory. Double-clicking on it from that location resulted with the same error.
Lastly, I tried opening the Extension Manager in Writer (Tools > Extension Manager) and clicked the Add button. Trying this method with /home/daniel/Downloads/dict-en-20260501.oxt or /home/daniel/.config/libreoffice/4/user/uno_packages/cache/uno_packages/lu132109gxx6t.tmp_/dict-en-20260501.oxt results in the same error.

