The Options button for remote content in the message header doesn't appear unless View/Message Body As is Original HTML. This is unrelated to Files & Attachments. Delete the entries for http and https (click the Action drop-down), and set Firefox as the default browser in Ubuntu settings.

Are we talking about the same thing? I don't think I'm referring to message body information. The screenshot is that of Files & Attachments. There is a box beneath that heading and in it, you can choose http or https and which browser to use. I can only choose in http, not https.

There should be no entries for http or https in Files & Attachments. TB uses the system default browser.

You mention the Options button for remote content, and this has nothing to do with default browser.

See attached screenshot. It shows a drop-down pick window when http is typed into the "Files and Attachments" option under the "Preferences" tab. You can see from the image that when http is chosen, there is an option what browser to use. They are listed there in the drop down.

However, if you type https in the same spot there is no "option" to choose which browser will be used.

Perhaps you are confusing my use of the word "options".

I mean that I can find now way to change which browser will be used when using https - clearly thunderbird provides the "option" to use another browser when http is in use as my screenshot shows. I'm only asking why isn't there a similiar "option" when hovering the mouse over the https entry?

Because I want to use https with Firefox but there is no drop down option to choose that because it only shows up in http.

There's no setting that will open http and https links in different browsers. Delete the entries and TB will open all links in the default browser.

https://support.mozilla.org/en-US/kb/hyperlinks-in-messages-not-working#w_check-that-no-application-is-specified-for-the-http-content-type

Thank you @sfhowes. I deleted the http setting and https is hard coded to chrome, which I don't want and there is no way to delete it. It's the only entry. With no option to delete it.

In Ubuntu 20.04 the default browser is set to Firefox. Which I want.

sudo update-alternatives --config x-www-browser There is only one alternative in link group x-www-browser (providing /usr/bin/x-www-browser): /usr/bin/google-chrome-stable Nothing to configure.

So now what? Pretty much ready to give up on Firefox and switch to Chrome - this shouldn't be so difficult and the interoperability is lame to say the least. All in a standard Ubuntu 20.04 install with no extensions in either Thunderbird or Firefox or Chrome.

The Firefox directory is within /home/user/firefox and contains the Firefox executable binary.

So to sum up: 1) In Thunderbird 78.11.0 (64-bit) under file & preferences https is set to chrome and I can't change or delete that entry. 2) In Ubuntu the default browser is set to Firefox. 3) In Ubuntu the listing for the default applications for browser is Firefox BUT the icon does not look normal, probably because their is no entry for it in x-www-browser.

Any help much appreciated.

If you can't delete the entry that points to Chrome, you can reset the entire list, i.e. remove all actions for all file types, by deleting or renaming handlers.json in the profile folder. Help/Troubleshooting, Profile Folder, Open Directory, close TB, delete or rename handlers.json. A new file will be created when TB restarts, and you will have to choose the associated app for attachment types like jpg, txt, pdf etc.

Thanks @sfhowes that worked!