Can't open or create a project in the web editor

[astrale-sharp]

Godot version:

3.2.4.rc1.official

OS/device including version:

❯ screenfetch
                                       astrale@Sharp
 MMMMMMMMMMMMMMMMMMMMMMMMMmds+.        OS: Linuxmint 20.1 ulyssa
 MMm----::-://////////////oymNMd+`     Kernel: x86_64 Linux 5.4.0-65-generic
 MMd      /++                -sNMd:    Uptime: 4h 19m
 MMNso/`  dMM    `.::-. .-::.` .hMN:   Packages: 3899
 ddddMMh  dMM   :hNMNMNhNMNMNh: `NMm   Shell: fish 3.1.0
     NMm  dMM  .NMN/-+MMM+-/NMN` dMM   Resolution: 1920x1080
     NMm  dMM  -MMm  `MMM   dMM. dMM   DE: Cinnamon 4.8.6
     NMm  dMM  -MMm  `MMM   dMM. dMM   WM: Muffin
     NMm  dMM  .mmd  `mmm   yMM. dMM   WM Theme: Mint-Y-Dark-Blue (Mint-Y)
     NMm  dMM`  ..`   ...   ydm. dMM   GTK Theme: Mint-Y-Dark-Red [GTK2/3]
     hMM- +MMd/-------...-:sdds  dMM   Icon Theme: breeze-dark
     -NMm- :hNMNNNmdddddddddy/`  dMM   Font: Ubuntu Condensed, 24
      -dMNs-``-::::-------.``    dMM   Disk: 719G / 1,1T (74%)
       `/dMNmy+/:-------------:/yMMM   CPU: Intel Core i3-2330M @ 4x 2.2GHz [60.0°C]
          ./ydNMMMMMMMMMMMMMMMMMMMMM   GPU: GeForce GT 630M
             \.MMMMMMMMMMMMMMMMMMM     RAM: 2668MiB / 3844MiB
                                      

Issue description:

I downloaded the demo.zip project example, loaded it into the editor and pressed "Start Godot editor", instead of opening the project it showed the project was missing.

Same thing happens if I try to start a new project from the online editor.

Steps to reproduce:
1 : download the demo.zip project
2 : try to import it

[Calinou]

Duplicate of #44754. See also godotengine/godot-proposals#2245 which details the exact steps you currently need to do to import a project in the web editor.