For playing around? I think, Rust is making some nice progress on the web front, and there are quite a few projects for mobile, too (fusing Flutter with Rust, for example). I don't know how far I would get, but that's what I'd love to do.
For freelancing purposes? It's unlikely that I'd create anything really big, so I would most likely go for a hybrid app on top of Cordova - if possible. WebDev still offers some of the best UI tooling around, and I know that stuff inside out. However, if that's not an option, maybe Object-Pascal or even Dart (Flutter). I wouldn't go as far as to use the native languages - too much trouble for freelancing imho. For web, NodeJS or PHP.
For corporate purposes? Preferably native development (Kotlin / Swift), but maybe also Dart (Flutter). On the web side, I'd go NodeJS or Kotlin. Rust might be nice, but is missing stable releases and SLA contracts...