Simple calendar setup but I get error 500 when browsing to calendarserver.sh

I'm just trying out sabre/dav on a virtual machine (debian 12, bookworm, running headless). The install instructions seem clear enough and I have the server.php delivering a sensible page. The next step is to get the calendar plugin installed and I followed these instructions. I created an sqlite database and created the tables. I also checked that the tables are there and at least one of them has contents. So far so good.

But when I browse to the calendar page it is blank and a quick look with my browser tools shows me I got an error 500 requesting the page. But there is nothing in the apache logs so I don't know what error I might have. My PHP is 8.2.26 and I think that's compatible (it certainly works with server.php). I tried groupwareserver.php with the same error 500 result.

I've likely done something wrong, but I can't see it. I think I don't need to do anything about authentication yet, but maybe I do?

In my server.php file I had to change the base uri:

$server->setBaseUri('/server.php');

before it would work. For calendarserver.php there is a base uri setting commented out. I tried setting that to

• the full path of the server file $baseUri = '/srv/sabredav/calendarserver.php';
• just /
• /srv/sabredav/

each of these resulted in the same error 500, which suggests the path isn't the real problem. I've also tried other ways to get the relevant error message logged eg adding this to the calendarsever.sh file:

ini_set('log_errors', 1); // enable error logging
ini_set('error_log', '/tmp/sabredav-errors.log' // specify error log file path

but no errors got logged.