I am using ddev based typo3 project and I cant manage my extensions, I cant find the get extensions, activate or any other action even if I am admin user
I looked in a lot of typo3 issues and dindt find the same problem and also the docs and gpt didnt help
Since your installation is based on composer, the only things left to the extension manager are to show a list of available and installed extensions and to provide possible actions assigned to those extensions.
So you can for example download the code as a zip file or execute a specific update script.
Anything else has to be done with composer, because otherwise you would be able to break the installation that was provided via composer.json and composer.lock