Devuan us a separate Debian with its own repositories (and presumably many packages patched to improve systemd-less life), while this is just replacing Systemd with OpenRC on a Debian system, while keeping Debian repos etc.

Well - it is an alternative to debian and in many ways is debian. But the counter-question is: why should debian users HAVE to use systemd? This is a much more fundamental question. Devuan solved it via forking. I think the proper way to handle this is to be able to offer both. I think gentoo went that approach. Debian went the "my-way-or-the-highway" route, which objectively is worse, even if understandable (less to maintain; see LFS/BLFS submitting to systemd finally in 2026: https://old.reddit.com/r/Gentoo/comments/1qy4xsc/might_gento... and https://www.phoronix.com/news/LFS-Dropping-SysVinit)