Dutch dictionary for flatpak version?

Spell check in my language is not available in the flatpak version. On the extension website there’s a beta for spellcheck and hyphenation rules, but that one has last been updated four years ago.

How can I get spell checking for Dutch (my native language) in LO when a recent dictionary is not provided for the flatpak version?

The version of LO which comes with my distribution is very old. The flatpak version is current.