Jbugy run composer why-not datlechin/flarum-link-preview 1.4.0
and/or composer require datlechin/flarum-link-preview:1.4.0 --dry-run
and copy the output here. It should give us more hints.
Looking at the data on Packagist, I see you need PHP 7.4 or greater and the PHP intl extension for the latest version. Version 0.1.4 is the latest that doesn't use the spekulatius/phpscraper
dependency and therefore doesn't require the PHP intl extension, making this the most likely cause.