I have not yet implemented anything on my live server (too much to do 
), but I have a setup on a test environment where I am currently running Cron from the host, which was very easy to set up.
*/5 * * * * docker exec -t -u www-data nextcloud php -f /var/www/html/cron.php
I have read some post about people having issues with the Background job status in NextCloud not being updated when running it this way, but it seems to be working for me at least.
I am going to try next setting up an additional container to run the Cron jobs, but honestly I’m not sure if it is worth the trouble.