I remember looking into GUI libraries for Python a while back and this one and qt came up.

However I ended up settling on making a Web UI served via FastAPI. I'm still happy about that decision but this one sounded really nice back then.

WebUI (assuming you're mean python-WebUI) doesn't actually include any UI. This is why PySimpleGUI is nice...you can make a button!

No, sorry, I wasn't referring to any library. I just meant a UI I made out of HTML, JavaScript and CSS.