Installing newer firefox on a Leap 15.4 installation, can it be done?

I have been using firefox 115.6.0esr on my laptop install of Leap 15.4.

I understand flatpak is a path to getting to at least 140.x. I have 
never used flatpak before.
*Should flatpak work for this task?*

I have flatpak-1.12.8-150400.3.3.1.x86_64 installed.

I am following a Google Search (AI) recipe to install newer firefox.

I am stuck on the command to add flathub repository for flatpak:

|flatpak remote-add --if-not-exists flathub https://flathub.org Warning: 
Could not update extra metadata for 'flathub': GPG verification enabled, 
but no summary found (check that the configured URL in remote config is 
correct) *How do I remedy this?* Thank you for any help. Allen |-- 

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