A Flarum extension to allow image uploading on thread and comment creation, supports multiple services like local storage and imgur.
composer require flagrow/flarum-ext-image-upload
Visit the settings tab of the extension in your admin to configure your image upload services.
During post creation, click the Attach button to select a file. Once you've chosen an image, upload will immediately start and based on the image size and your connection will take some time to complete.