Damn I was worried for a second there, fearing some sort of falling out with the community. But this is awesome news! Ladybird is a far more important project to focus on imho.
Given that it dropped serenity as a target, it does seem there is something more to this story…
I've been working on projects myself where the primary target switched, because I noticed it's a bit draining to keep supporting something "just" because I love it. Dropping a target usually doesn't mean it cannot be used there anymore, but simply that you don't feel comfortable guaranteeing support.
I don't know if that's the case here, only that it doesn't necessitate bad feelings.
Given that it was also stated that it won't be self-contained anymore that's also a very good technical reason. And I totally get that if you want to create a new browser with a new layout engine not wanting to re-invent every audio, video, image decoder, not wanting to reinvent all the wheels makes it already a huge project and I'd assume it's hard to guarantee all of these things will also work and compile on Serenity, which despite doing an amazing job at porting might get stuck here and there. I mean, see the OpenBSD and Rust(up) story.