Although the original Project Oberon was great for its day, one should have a look at Oberon System 3 and Blue Bottle (AOS), which evolved Oberon (language) into Active Oberon (language), while offering a much more modern L&F.
Unfortunately the www.ocp.inf.ethz.ch seems to have been moved out of Internet. It had quite some information about Bluebottle, although there are some Github mirrors like this one:
Is Active Oberon considered a canon (for lack of a better term) successor to Oberon07 or is it more like Component "Pascal" and just a spin off from an Oberon version?
=> Active Oberon
=> Oberon.NET => Zonnon
=> Oberon-07 (multiple iterations until 2016)
From features think Go (Oberon), D/C# (Active Oberon).
Active Oberon provides features for manual memory management (untraced references), async/await (active objects hence the name), lightweight generics, interfaces, exceptions.
Some surviving info regarding System 3:
https://www.drdobbs.com/architecture-and-design/oberon-syste...
https://www.semanticscholar.org/paper/Oberon-with-Gadgets-A-...
https://sourceforge.net/p/nativeoberon/wiki/Home/
https://www.semanticscholar.org/paper/Project-Oberon-the-des...
Some surviving info regarding Bluebottle (AOS):
https://os-projects.eu/oberon-system
https://www.linux.org.ru/gallery/screenshots/4163239
Unfortunately the www.ocp.inf.ethz.ch seems to have been moved out of Internet. It had quite some information about Bluebottle, although there are some Github mirrors like this one:
https://github.com/cubranic/oberon-a2
The doc directory has lots of nice info.
The latest version of Active Oberon manual as of 2019:
http://cas.inf.ethz.ch/news/2