It is recommend to use a recent version from Github https://github.com/FriendsOfTYPO3/extension_builder.
The latest version of the master branch does not work for the current LTS version of TYPO3 and I don't find any tags 9.x at all on Github.
In the extension manager the master branch identifies already as 9.10.0 so I have hope there is a working version for TYPO3 9.5 LTS. Which version is it?
If there is no working version for 9.t LTS, what is your workaround?
As of today a working approach for TYPO3 9.5 LST is this:
Latest commit of master:
ad22d356546794cecfe436ad2d3e3290933f3693
Manual fix of the save bug as given here by the user qbadev:
https://github.com/FriendsOfTYPO3/extension_builder/issues/178