Hi.
I was trying to find a way to do this and I would like to describe the solution found based on the last suggestion.
According with this method, you can hide the buttons by override the CSS. To do this you can install an app called “Custom CSS” and add a specific CSS code to hide the buttons in custom settings.
So:
- Install “Custom CSS” app:
-
Go to the Configuration/Theming options and find the configuration of Custom CSS .
-
Add this lines in Custom CSS box settings to override CSS by id and hide the buttons:
#jsxc-submit-wrapper { display: none; }

4. Click in save button.
Then the buttons must have been hidden.
I hope this helps.
Reference:
https://help.nextcloud.com/t/theming-custom-css/
https://marksheet.io/css-priority.html