Installation not possible on CiviCRM 5.80.1

[fynngodau]

We are trying to install the project60 membership extension on our fresh, standalone instance of CiviCRM 5.80.1, but unfortunately the installation fails with following error message being displayed in the browser:

 Fatal error: Uncaught Error: Cannot access protected property Smarty\Smarty::$template_dir in /var/www/html/core/packages/smarty5/Smarty.php:37 Stack trace: #0 /var/www/html/ext/org.project60.membership/membership.civix.php(99): Smarty->__get('template_dir') #1 /var/www/html/ext/org.project60.membership/membership.civix.php(129): _membership_civix_civicrm_config() #2 /var/www/html/ext/org.project60.membership/membership.php(85): _membership_civix_civicrm_install() #3 /var/www/html/core/CRM/Extension/Manager/Module.php(71): membership_civicrm_install() #4 /var/www/html/core/CRM/Extension/Manager/Module.php(39): CRM_Extension_Manager_Module->callHook(Object(CRM_Extension_Info), 'install') #5 /var/www/html/core/CRM/Extension/Manager.php(296): CRM_Extension_Manager_Module->onPreInstall(Object(CRM_Extension_Info)) #6 /var/www/html/core/api/v3/Extension.php(42): CRM_Extension_Manager->install(Array) #7 /var/www/html/core/Civi/API/Provider/MagicFunctionProvider.php(89): civicrm_api3_extension_install(Array) #8 /var/www/html/core/Civi/API/Kernel.php(153): Civi\API\Provider\MagicFunctionProvider->invoke(Array) #9 /var/www/html/core/Civi/API/Kernel.php(79): Civi\API\Kernel->runRequest(Array) #10 /var/www/html/core/api/api.php(147): Civi\API\Kernel->runSafe('Extension', 'install', Array) #11 /var/www/html/core/CRM/Admin/Form/Extensions.php(187): civicrm_api3('Extension', 'install', Array) #12 /var/www/html/core/CRM/Core/Form.php(646): CRM_Admin_Form_Extensions->postProcess() #13 /var/www/html/core/CRM/Core/StateMachine.php(144): CRM_Core_Form->mainProcess() #14 /var/www/html/core/CRM/Core/QuickForm/Action/Next.php(43): CRM_Core_StateMachine->perform(Object(CRM_Admin_Form_Extensions), 'next', 'Next') #15 /var/www/html/core/packages/HTML/QuickForm/Controller.php(203): CRM_Core_QuickForm_Action_Next->perform(Object(CRM_Admin_Form_Extensions), 'next') #16 /var/www/html/core/packages/HTML/QuickForm/Page.php(103): HTML_QuickForm_Controller->handle(Object(CRM_Admin_Form_Extensions), 'next') #17 /var/www/html/core/CRM/Core/Controller.php(356): HTML_QuickForm_Page->handle('next') #18 /var/www/html/core/CRM/Core/Page/Basic.php(364): CRM_Core_Controller->run() #19 /var/www/html/core/CRM/Core/Page/Basic.php(170): CRM_Core_Page_Basic->edit(1, NULL) #20 /var/www/html/core/CRM/Admin/Page/Extensions.php(110): CRM_Core_Page_Basic->run() #21 /var/www/html/core/CRM/Core/Invoke.php(319): CRM_Admin_Page_Extensions->run(Array, NULL) #22 /var/www/html/core/CRM/Core/Invoke.php(71): CRM_Core_Invoke::runItem(Array) #23 /var/www/html/core/CRM/Core/Invoke.php(36): CRM_Core_Invoke::_invoke(Array) #24 /var/www/html/core/Civi/Standalone/WebEntrypoint.php(79): CRM_Core_Invoke::invoke(Array) #25 /var/www/html/core/Civi/Standalone/WebEntrypoint.php(20): Civi\Standalone\WebEntrypoint::invoke() #26 /var/www/html/index.php(35): Civi\Standalone\WebEntrypoint::index() #27 {main} thrown in /var/www/html/core/packages/smarty5/Smarty.php on line 37

I couldn't find information about this extension being unsupported on recent versions, hence I am hoping for a way to resolve this problem.

[bjendres]

@fynngodau If there's no funding, maybe you can fix this yourself following this guide and creating a PR?

[TheAssassin]

A few pointers surely would be appreciated...