cant install flash player into firefox

[robert rottermann]

Hi there

on my ubuntu v18.10 box I try to install a flash firefox plugin.

Firefox is Firefox Quantum 63.03 (64-bit)

This is what I did:

1. I firefox I navigated to a site (BigBlueButton) that needs flash to operate.

2. I get: You need Adobe Flash installed and enabled in order to use this client.

3. I Donload Flash Version 31.0.0.153

When I try to install with "Ubuntu Software"

4. I select "Ubuntu Software" as to install

5. An error "Failed to install: Not supported"

When I Try to use "Apt Url"

4. I Select "Apt Url"

5. Error: Unknown channel 'cosmic-partner'


Can anyone please give me a hint how to proceed?

Thanks

Robert