It appears that all the binaries in this package are not for the architecture that the package was made for.
I have done (Debian 11 under Chrome-OS):
$ sudo flatpak install flathub org.blender.Blender
# success
$ flatpak run org.blender.Blender
/app/bin/blender: line 3: /app/blender/blender: cannot execute binary file: Exec format error
When I do this,
$ flatpak info org.blender.Blender
I get
Blender - Free and open source 3D creation suite
ID: org.blender.Blender
Ref: app/org.blender.Blender/aarch64/stable
Arch: aarch64
Branch: stable
Version: 3.2.1
License: GPL-3.0
Origin: flathub
Collection: org.flathub.Stable
Installation: system
Installed: 725.1 MB
Runtime: org.freedesktop.Platform/aarch64/21.08
Sdk: org.freedesktop.Sdk/aarch64/21.08
After some search, I found that the libraries that come with the flatpak image still have the x86-64 architecture:
$ cd /var/lib/flatpak/app/org.blender.Blender/aarch64/stable/active/files/blender/lib
$ file *
libglapi.so: symbolic link to libglapi.so.0
libglapi.so.0: symbolic link to libglapi.so.0.0.0
libglapi.so.0.0.0: ELF 64-bit LSB shared object, x86-64, version 1 (SYSV), dynamically linked, BuildID[sha1]=9c2f38d28b00a9ee8c9a01475f3de95b154cd8cf, stripped
libGL.so: symbolic link to libGL.so.1
libGL.so.1: symbolic link to libGL.so.1.5.0
libGL.so.1.5.0: ELF 64-bit LSB shared object, x86-64, version 1 (GNU/Linux), dynamically linked, BuildID[sha1]=5d6e9837d9d8e483528222545d1682eb82dc350f, stripped
libGLU.so: symbolic link to libGLU.so.1.3.1
libGLU.so.1: symbolic link to libGLU.so.1.3.1
libGLU.so.1.3.1: ELF 64-bit LSB shared object, x86-64, version 1 (SYSV), dynamically linked, BuildID[sha1]=2ff97a276fd5a54bc65159375eaa8ca899a283fa, stripped
$ cd ../blender
$ file blender
blender: ELF 64-bit LSB executable, x86-64, version 1 (SYSV),
dynamically linked, interpreter /lib64/ld-linux-x86-64.so.2, for GNU/Linux 2.6.32, BuildID[sha1]=b522c01871bc5782ef11c7af9cfa245957aa2156, stripped