A lot of errors after successful installation

Hi guys,

I installed version 21 on a Ubuntu 20.04, mysql, php 7.4.
Everything ok with the installation. However, the dashboard is invisible and only some apps work. Calendar, dashboard, etc. I cannot create users. I got a bunch of errors.

vel App Message Time
Fatal no app in context Error: Call to undefined method OC\AllConfig::isGlobalScaleEnabled()

2021-03-18T15:45:37-0500
Fatal no app in context Error: Call to undefined method OC\AllConfig::isGlobalScaleEnabled()

2021-03-18T15:45:36-0500
Fatal no app in context Error: Call to undefined method OC\AllConfig::isGlobalScaleEnabled()

2021-03-18T15:45:34-0500
Fatal no app in context Error: Call to undefined method OC\AllConfig::isGlobalScaleEnabled()

2021-03-18T15:45:33-0500
Fatal no app in context Error: Call to undefined method OC\AllConfig::isGlobalScaleEnabled()

2021-03-18T15:45:31-0500
Error index OCP\Files\NotPermittedException: Could not create folder

2021-03-18T15:30:43-0500
Error no app in context Error: Call to a member function getContainer() on null

2021-03-18T15:30:23-0500
Error PHP Error: Undefined index: mail at /var/www/html/nextcloud/lib/private/AppFramework/Bootstrap/RegistrationContext.php#421

2021-03-18T15:30:23-0500
Error no app in context Error: Call to a member function getContainer() on null

2021-03-18T15:30:23-0500
Error PHP Error: Undefined index: workflowengine at /var/www/html/nextcloud/lib/private/AppFramework/Bootstrap/RegistrationContext.php#404

Can anybody help?
Thank you.