Hopefully the thread starter found the answer by now, but this list of improvements and bug fixes on flathub.org might answer the question for others.
https://flathub.org/apps/details/io.lmms.LMMS
Perhaps some users of the flatpak version can advise if there is anything missing.
https://flathub.org/apps/details/io.lmms.LMMS
Perhaps some users of the flatpak version can advise if there is anything missing.