FWIW not only is the project alive (last commit 17 hours ago) but distribution too (cf links above) and project management too (cf e.g. https://github.com/orgs/LMMS/projects/1 as example of complex set of tasks mostly done toward a major release).
So... I'm not going to give people working on LMMS any advice, but of course I hear you, and OP, when it shows for people who aren't deep into it a project that seems abandoned.
I do not know no why the project is in that state but what I hope I have shown is that for sure it's very much active.