Here's a guide to changing Joomla templates via PhpMyAdmin, please follow the steps below:
1. Login Cpanel
2. Click Phpmyadmin in the Cpanel main menu
3. Select the website database
4. Click jos_templates_menu
5. After that there will be two tables then click edit on the far left of the first row in the image above
6. Replace namatemplate with the new *template or the one you want to use
7. Click Go/Save
8. Also, pay attention to the second table. Make sure the template column is filled with "khepri", if it is not filled then when the admin will access the Administration room (name.domains/administrator) it will display a white page (nge-blank). This also needs to be considered for those of you whose joomla website has been hacked, not infrequently hackers modify this second row table with the aim of turning off admin access to the joomla website administration space.
9. Clear cache browser
10. Now your website appears with the new template and you can see the login screen to your wordpress dashboard as usual.
Note:
*new template is the name of your template folder in file manager -> public_html -> templates -> template folder name
To add a new template manually, upload the template you created or downloaded to the public_html -> templates folder, if the template is .zip then right-click file -> extract