Abandoned package

xiaodu

Two obsolete packages appeared when running composer install on a new installation

Package laminas/laminas-zendframework-bridge is abandoned, you should avoid using it. No replacement was suggested.
Package swiftmailer/swiftmailer is abandoned, you should avoid using it. Use symfony/mailer instead.

luceos

xiaodu the packages in question are not extensions. As long as these warnings do not mention an extension, you can ignore them.

To give you a little background information, the packages you mention are indeed abandoned, but they are part of packages Flarum uses (called upstream dependencies). Flarum cannot easily upgrade these dependencies while remaining backward compatible, so this is usually done during a new major version release (v1.x to v2.x). And although these packages are abandoned, they still work.