Problems installing H5P on moodle - filesystem?

Hello everbody.

I have run into several problems trying to install H5P on moodle.

I have made a PDF with print screens, describing the steps taken to install and the problems I have run into, but cannot upload it. Here goes a summary of the problem:

I am trying to get H5P working on a moodle server. The moodle serves my secondary school, and I am a computer science teacher in charge of the school’s systems. It runs on a up to date ubuntu server, locally managed and available online. I manage the moodle server (ver. 3.5+) online with an administrator account, and the ubuntu server (ver. 18.04) locally (school LAN, through SSH), with admin/root account. Ubuntu is up-to-date. Both ubuntu and moodle were set up by me, on a dedicated HP Enterprise server.

Installing H5P from moodle.org gives HTTP error 500.

installing manually works fine. Accessing H5P libraries on the plugins list on moodle gives HTTP error 500 again.

There are no installed libraries avaliable. Manually instaling doesn't work either.

Trying to add H5P content on a subject is impossible ""Error, unable to load libraries".

I think the problem resides on the ubuntu filesystem permissions settings. They are as follows:

The moodle site is on /var/www/html. The recursive permissions of the html folder are: owner is root, can RW; group is www-data, can RW.

 The moodle data is on /var/moodledata. Owner is www-data can RW; group is www-data, can RW

The ubuntu server and the moodle software were installed as usual, with the default filesystem permissions, which I have changed as described above, to try to solve the problem.

Any help will be very much appreciated. Thanks!