[mikewarot]

Lazarus is a cross platform and open source GUI builder based on Free Pascal. If you can handle begin and end instead of { }, you'll get used to it fairly quickly. As a bonus, it does strings that you never have to allocate or deallocate, and can handle a gigabyte of data.

I've run Lazarus on a Raspberry Pi Zero W (the old one), Linux, and Windows.

[thijsvandien]

As much as I like Lazarus, I wouldn't recommend it for complex data visualizations by someone skilled in web tech.