1 I'm on a Chromebook does that still work??
2 If so how do I open it??
1. Chromebooks can open Linux apps so yes.
2. I'm not sure since I don't own a Chromebook but I found this https://support.google.com/chromebook/answer/9145439?hl=en
Yup, from the linux container just type "chmod u+x Tiled-1.4.3-x86_64.AppImage" for example.
Then run it. For example "./Tiled-1.4.3-x86_64.AppImage"
(You don't have to type out the whole file name, just hit TAB for autocomplete.)