Lemmy subscription from remote instance not working properly over Friendica

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Bug Description

Attempting to use the "Subscribe" button on Lemmy instances that allow for external subscription fails when pointing towards a Friendica instance.

Steps to Reproduce

Go to any Lemmy instance running version 0.19.5 or later. Ensure that you're not currently logged in.
Go to a group, click "Subscribe".
On the pop-up "Subscribe to Remote Instance" field, type your Friendica instance's URL. (For this case, we will use friendica.example.net as our example URL.)
Click on "Fetch Community".

Actual Result:

The page is redirected to a URL of the form https://friendica.example.net/activitypub/externalInteraction?uri=https%3A%2F%2Flemmy.example.com%2Fc%2Fmaingroup, which is not recognized by Friendica. The following pop-up appears:

Exception thrown in /var/www/friendica/src/Module/HTTPException/PageNotFound.php:49
Stack trace:
#0 /var/www/friendica/src/BaseModule.php(250): Friendica\Module\HTTPException\PageNotFound->content()
#1 /var/www/friendica/src/Module/HTTPException/PageNotFound.php(80): Friendica\BaseModule->run()
#2 /var/www/friendica/src/App.php(677): Friendica\Module\HTTPException\PageNotFound->run()
#3 /var/www/friendica/index.php(46): Friendica\App->runFrontend()
#4 {main}

Expected Result:

The remote subscription should be recognized as such, and the system should then follow the standard subscription workflow.

Screenshots

imagen

Platform Info

Friendica Version: 2024.06-dev (but can be also replicated on the latest stable version)

Friendica Source: Git repository, YunoHost

PHP version: 8.2

SQL version: 10.5.23-MariaDB

friendica / friendica