[pzo]

You have to give credit to react time which seems that started this paradigm of declarative and reactive ui frameworks. After that you got react native, flutter, jetpack compose and now swift ui. As for declarative (but not reactive) ui prior art is also Qt qml.

[sandeepc24]

Also have a look at https://fsprojects.github.io/Fabulous/

[thomasjames]

Both looked kind of like GTK (in a non-verbose language like Python) to me, too. Maybe I am seeing things.