Unable to install Tor browser on Ubuntu 25.04 for Raspberry Pi 5 with flatpak

I tried the instruction in the following page.
https://linux.how2shout.com/how-to-install-tor-browser-on-ubuntu-22-04-lts-jammy/#7-install-flatpak

$ sudo apt install flatpak -y
flatpak is already the newest version (1.16.0-2).
Summary:                    
  Upgrading: 0, Installing: 0, Removing: 0, Not Upgrading: 0

$ sudo flatpak remote-add --if-not-exists flathub https://flathub.org/repo/flathub.flatpakrepo

$ flatpak install flathub com.github.micahflee.torbrowser-launcher -y
Looking for matches…
error: Nothing matches com.github.micahflee.torbrowser-launcher in remote flathub

Any idea what is wrong?
It is running on Ubuntu 25.04 with Raspberry Pi 5