Thank you. .. one step ahead... it says now 'Whoops, looks like something went wrong.'
Did restart apache, but same prob.
Also changed storage, bootstrap/cache, public/assets/user directories, config/database.php and config/app.php to www-data
Hope I did not miss some manual somewhere?
error.log is

[core:notice] [pid 1714] AH00094: Command line: '/usr/sbin/apache2'

'/usr/sbin/apache2' path is ok. '[core:notice] [pid 1714] AH00094:' don't tells too much.
Any idea on that error, do I need to have laravel installed for IdeaSpaceVR to work?

Hi, tried yesterday to install your IdeaSpace on my local machine (ubuntu), sadly blank page on FF, HTTP ERROR 500 on Chronium. In logs apache has:

PHP Fatal error:  Uncaught UnexpectedValueException: The stream or file "/var/www/html/vr/storage/logs/laravel.log" could not be opened: failed to open stream: Permission denied in /var/www/html/vr/vendor/monolog/monolog/src/Monolog/Handler/StreamHandler.php:107\nStack trace:\n#0 /var/www/html/vr/vendor/monolog/monolog/src/Monolog/Handler/AbstractProcessingHandler.php(37): Monolog\\Handler\\StreamHandler->write(Array)\n#1 /var/www/html/vr/vendor/monolog/monolog/src/Monolog/Logger.php(336): Monolog\\Handler\\AbstractProcessingHandler->handle(Array)\n#2 /var/www/html/vr/vendor/monolog/monolog/src/Monolog/Logger.php(615): Monolog\\Logger->addRecord(400, Object(Symfony\\Component\\Debug\\Exception\\FatalErrorException), Array)\n#3 /var/www/html/vr/vendor/laravel/framework/src/Illuminate/Log/Writer.php(202): Monolog\\Logger->error(Object(Symfony\\Component\\Debug\\Exception\\FatalErrorException), Array)\n#4 /var/www/html/vr/vendor/laravel/framework/src/Illuminate/Log/Writer.php(113): Illuminate\\Log\\Writer->writeLog('error', Object(Symfony\\Component\\De in /var/www/html/vr/vendor/monolog/monolog/src/Monolog/Handler/StreamHandler.php on line 107

Any idea what went wrong?
I think I have all requirements installed (https://ideaspacevr.org/documentation/1.2)