I found a solution to the problem with Chrome’s built-in translator so I removed that from the first post. The problem was on my side in the firewall rule. This greatly confused me with inconsistent manifestations.
There are still problems with the google translate site (I already found questions about this problem here) and problems with the official google translate extension for browsers that do not have a built-in translator. This is less of a problem, but still a problem for me because I am not using Chrome, but using the Brave browser due to security issues.
At the moment, I can say that the official google translate plugin cannot translate this forum, but forum.ghost.org does translate without problems. Perhaps the matter is in what forum settings or styles.
PS I will try to check more sites on Discourse to understand when there is a problem.