I noticed the official fastText repository was archived Mar 19, 2024 and is thus no more maintained at all.

Annif already installs fastText from the fasttext-wheel PyPI project, which builds code from https://github.com/messense/fasttext-wheel (Annif initially switched to that because of this installation issue).

At some point installation from the fasttext-wheel project probably won't work. In the fastText mailing list someone already reported a compatibility issue with NumPy 2.0. Actually when I now try to install the fasttext backend dependencies of Annif on Python 3.12 on my laptop, Poetry complains Unable to find installation candidates for fasttext-wheel (0.9.2) (two weeks ago, but after NumPy 2.0 release, CICD successfully installed fastText).

If we want retain the fasttext backend in Annif for a long term, some alternative provider for fastText should be found. There are a number of more or less active fastText forks.