Couple things I've seen in this space looking around the past couple weeks...
Flutter made a different engine called Impeller[0] which is replacing Skia. Which is a bit surprising as an ignorant outsider. I hope that works out.
Rive (https://rive.app), is a new animation tool that targets multiple platforms including web and their CEO Guido Rosso gave a great interview on School of Motion[1] about how they are building an animation first vector engine. There is a side by side demo at 46:56[2] of Skia, Impeller and Rive.
Upcoming there's also Vello[0][1] by Raph Levien, who has a bunch of experience w/ font rendering at Google. He's also working on a Rust UI library[2] and has a great talk on compute shaders[3].
I've been following Rive for a while, it's an interesting approach. I think it was a response to the fact that Lottie was tied to AdobeXD (I think?). I'm not sure if Rive's renderer is open source though.
Completely ignorant question: what's the issue with Cairo? I know it has had a hard time getting maintained but is there any article or blog talking about how it works or how it doesn't work? I've never used it directly but I'm super curious to know more !
> There was an attempt at making Cairo support GPU rendering, which did not work particularly well due to the library being designed around stateful operation based upon the PostScript model—resulting in a convenient and familiar API, great output quality, but hard to retarget and with some particularly slow corner cases. Meanwhile, other web engines have moved more work to the GPU, including 2D rendering, where many operations are considerably faster.
0: https://www.youtube.com/watch?v=mmW_RbTyj8c
1: https://github.com/linebender/vello
2: https://www.youtube.com/watch?v=zVUTZlNCb8U
3: https://www.youtube.com/watch?v=DZRn_jNZjbw