The error message unknown variable 'thread_concurrency=8' suggests that the MySQL server is attempting to start with the thread_concurrency variable set to 8, but this variable is not recognized.
This error can occur if the thread_concurrency variable has been removed or renamed in a newer version of MySQL, or if it has been misspelled in the configuration file.
To fix this error, you will need to edit the MySQL configuration file (my.cnf or my.ini) and remove or correct the thread_concurrency variable. If you are not sure where this file is located, you can use the locate command to find it:
locate my.cnf
Once you have found the configuration file, open it in a text editor and remove or correct the thread_concurrency variable. Then, try starting the MySQL server again.
If you are not sure what value to use for the thread_concurrency variable, or if you want to remove it altogether, you can consult the MySQL documentation or consult with a MySQL expert for guidance.