LiveReload of Spring Boot Vaadin App in Firefox doesn't work

The LiveReload feature doesn’t work with Firefox.
I’ve setup a Spring Boot App according the [Tutorial]
(https://vaadin.com/learn/tutorials/modern-web-apps-with-spring-boot-and-vaadin/importing-running-and-debugging-a-java-maven-project-in-intellij-idea#_enabling_live_browser_reload)
and install the AddOn LiveReload in Firefox 86.0 (64-Bit) for MacOs.
The Spring Boot has the devtools inclusive LiveReload enabled, the log mentioned
LiveReload server is running on port 35729
If I modify the UI for the test app from the tutorial and change e.g. the label for the given text field, the Spring Boot App restarts but the html page in FF isn’t reloaded. Only a small notification “Vaadin development mode initialized” is visible in the lower right corner of the FF windows.
In Googlr Chrome (Version 89.0.4389.72 (x86_64)) for MacOs everything work as expected.

How can I enabled LiveReload for Firefox too ?

Kind regards
Dominik