I followed this guide:
I logged into the Plesk control panel as an administrator, clicked "Service Plans" in the left vertical menu, selected the desired plan (this is the only plan that has Subscriptions at the moment), went to the "Hosting Parameters" tab, unchecked "Permanent SEO" - safe 301...
After unchecking "Permanent SEO-safe 301 redirect from HTTP to HTTPS" and pressing the "Update & Sync" button, the redirect continues to work. I go to the nginx.conf file of the test site and see the following lines in it:
server {
listen xxx.xxx.xxx.xxx:80;
server_name xxxxxxxxxx.xxx...