[Joomla 4.0] CiviCRM cannot be installed on Joomla 4.0 alpha
Tested with Joomla 4.0 alpha 11 and CiviCRM 5.16.2.
The installer fails due to several methods that are deprecated in Joomla 4.0 in these files:
script.civicrm.phpconfigure.php
See PR #52 for detail of what is deprecated.
When those are resolved and CiviCRM has been installed then it will not be possible to log in to the Joomla Administrator backend. This is due to the CiviCRM User Management plugin's admin/plugins/civicrm/civicrm.php. Again see PR #52, which resolves this, for detail.
After the above are resolved, there are some styling issues and the new CiviCRM doesn't get positioned nicely with Joomla 4.0 but those issues are out of scope for this issue.