On the other hand it should be a simpler solution to install version 2.3.7 and to import the content of the old forum. There is only one relevant change in the settings table in version 2.3.7 you have to checkafter moving the settings from the old to the new forum. Search for the setting temp_block_ip_after_repeated_failed_logins and set it to a value of 10 minutes in the case it has in reality a value different from 0. (see therefore the wiki page about the configuration settings)

I choosed that option. Now, I have 2.3.4 and 2.3.7 in parallel. I had to change the database prefix from the 2.3.4 backup files before restoing it into 2.3.7. Also, I checked the temp_block_ip_after_repeated_failed_logins after restoring. Looks o.k. so far, now I try the step to 2.4.19.1

N.