Solved.
Please see this thread for the issue. As I assumed it was one of my settings: htaccess rewrite rule to prevent DELETE request - options
The problem was this… For 20 years I have prevented the DELETE request via a global htaccess file for apache. This has not been a problem for other PHP sites (Wordpress), but is a problem with NextCloud.
What I have been using:
RewriteCond %{REQUEST_METHOD} ^(DEBUG|DELETE|HEAD|TRACE|TRACK) [NC]
RewriteRule ^(.*)$ - [F,L]
So I have changed the condition and rule to:
RewriteCond %{REQUEST_METHOD} ^(DEBUG|HEAD|TRACE|TRACK) [NC]
RewriteRule ^(.*)$ - [F,L]
And now I can delete files and photos. But I really don’t love this.