I just completed a fresh install of NextCloud 20 in a HyperV VM with 2 cores and 4GB RAM on SSD. It was unbearably slow e.g. minute to load each page. After going through some forum posts on here I found the best solution was to disable apps one-by-one to find out if one of the apps has an issue. I found that the app “Collabora Online” was the cause and after disabling it the page loading speed was down to milliseconds.
I experienced a very similar issue but after a successful update from NC19 to 20.
User interface became unusable, it took over 30sec before any page would load and disabling CollaboraOnline was an immediate remedy.
Running a code check on the reachdocuments app gives:
root@nextcloud:/var/www/nextcloud# sudo -u www-data php occ app:check-code richdocuments
Analysing /var/www/nextcloud/apps/richdocuments/appinfo/app.php
1 errors
line 51: OC_Helper - Static method of private class must not be called
Analysing /var/www/nextcloud/apps/richdocuments/lib/Controller/DocumentController.php
1 errors
line 565: OC_Helper - Static method of private class must not be called
Analysing /var/www/nextcloud/apps/richdocuments/lib/Controller/WopiController.php
1 errors
line 349: OC_User - Static method of private class must not be called
Analysing /var/www/nextcloud/apps/richdocuments/lib/Service/UserScopeService.php
2 errors
line 65: OC_Util - Static method of private class must not be called
line 66: OC_Util - Static method of private class must not be called
App is not compliant