Feedburner is a walking dead. You'll have to find another valid source for your feed. I don't think that this is a Thunderbird problem.

https://support.mozilla.org/en-US/questions/1402266 and https://support.mozilla.org/en-US/questions/1380653 seem to indicate otherwise.

i've got another URL that is generating a "The Feed URL is not authorized" error and it's not from feedburner. the fact that two DIFFERENT URLs generate the same message points more towards thunderbird than it does to https://charliehebdo.fr/feed or feedburner. is someone going to do something about this?

yeah, they are going to change the user agent string. string again. If the change for mail will affect RSS I have no idea. https://bugzilla.mozilla.org/show_bug.cgi?id=1114475

But it does point to the pref general.useragent.override accessed via the config editor where you can set the entry to any text string you like. Armed with a list if user agent string like this you can say your visiting with whatever browser you like.

Fundamentally user agents are in decline, so no one is likely going to look at what you conceive to be a problem. See the discussion on client hints as to the future. I guess, either these sites need to update, or go under. https://developers.whatismybrowser.com/learn/browser-detection/client-hints/detect-windows-11-client-hints

the fact that two DIFFERENT URLs generate the same message points more towards thunderbird than it does to https://charliehebdo.fr/feed or feedburner.

When following the link in a browser, it offers to download a .rss file. I don't know what format a .rss file is. I didn't check, and I did not attempt to download it either.

For a valid feed, there should be a .xml file, which a browser does show. So I don't think the link you provided is a valid feed URL. If you find a different feed reader which works with it, let me know.

yeah, they are going to change the user agent string. string again. If the change for mail will affect RSS I have no idea.

That change will not go into TB102.

Update

The https://charliehebdo.fr/feed URL does indeed work with Feedly. I don't know why it wouldn't work with Thunderbird. You may want to raise a bug in Bugzilla. https://bugzilla.mozilla.org/

https://charliehebdo.fr/feed works here with Thunderbird V102 on windows 10.

https://feeds.feedburner.com/LICD validates with w3c as a valid feed, with some issues https://validator.w3.org/feed/check.cgi?url=https%3A%2F%2Ffeeds.feedburner.com%2FLICD

when trying to import into Thunderbird the error console shows.

22:33:17.557 XHRGEThttps://feeds.feedburner.com/LICD [HTTP/3 403 Forbidden 330ms]

GET https://feeds.feedburner.com/LICD Status 403 Forbidden

So I tried toddling off to the feedburner.com url in my browser. It asked me to authenticate. So I am guessing you can not connect to feedburner.com for a feed unless you are authenticated hence the 403 error.

But I really have no idea why feedburner is refusing access, I am guessing. I do know if I add the feed in the response from feedburner https://leasticoulddo.com/feed it adds to Thunderbird without issue.

thudnerbird 102.4.2, kubuntu 22.04

yesterday, https://charliehebdo.fr/feed didn't work, and generated a "The Feed URL is not authorized" error.

today, https://charliehebdo.fr/feed works fine now. i click the "Verify" button, and it said "The feed has been authorized"...

nothing about https://charliehebdo.fr/feed has changed, but yesterday, thudnerbird said that it wasn't authorised, and today, it says it is.

i don't know how thudnerbird deals with user-agent strings, or whether or not user-agent strings are "in decline", but i do know that thudnerbird is being inconsistent, and the other sites i have tried are not being inconsistent.

and, today, https://charliehebdo.fr/feed doesn't work, and generates a "The Feed URL is not authorized" error... this is not an issue with charlie hedbo, this is an issue with thudnerbird.

Same issue here, with https://feeds.feedburner.com/HaveIBeenPwnedLatestBreaches

Adding: Error console of Mozilla Thunderbird is telling me in https://feeds.feedburner.com/HaveIBeenPwnedLatestBreaches is incorrectly formed:

XML parsing error: incorrectly formed
Location: https://feeds.feedburner.com/HaveIBeenPwnedLatestBreaches
Line 1, column 12:

(The above was translated from Dutch version of Thunderbird)

Do not know for sure, but guess the contents of that line is:

<rss version="2.0">

Seemingly, there is a bit of inconsistency here: while trying to add the URL it is stated there is an authorization issue with the feed-URL, but referring to the error console it is reported as above. Guess that is not quite the same.

Also, I have contacted Have I Been Pwned for this. Response (from the owner and founder of that site himself) was, that the URL at stake was validated here, at W3.

So, same validation as Thunderbird could do, once an RSS feed has been added to it.

Running this myself within that validator, I can see that there are congratulations for a valid RSS feed, but there is a recommendation concerning this feed, too, as to "interoperability with the widest range of feed readers".

Well, after having read the topics within support.mozilla.org and bugzilla.mozilla.org as to all of this (for the links on topic see several of these above), and seeing that TB is not really willing to resolve this issue over a couple of years now, I have resorted to the workaround given by walmar.postbox (in Comment 4 in the Bugzilla thread).

So, from now on I will add to TB newly found RSS-feeds through that (adequately working) mechanism within AutoHotkey (and discard of the TB mechanism for this, being this inconsistent).