Getting iOS to sync reminders on local NextCloudPi

Nextcloud version: via NextCloudPi v1.30.0. Running as a docker image, local access only.
Operating system and version: OpenMediaVault 4.1.35-1 (Arrakis)
Hardware: Odroid HC-1
Kernel: Linux 4.14.150-odroidxu4

The issue you are facing:
I am trying to access my NextCloud reminders via iOS 14.0.1. NextCloud calendar and contacts sync fine, but reminders do not sync. This looks like the same issue described here:

I’m running a NextCloudPi docker image and have it configured for local access only (no port forwarding). Based on the info described in the issue above, I think I want to:

  1. Configure my NextCloudPi self-signed certificate to be compliant with the new iOS requirements (

  2. Load this certificate (xxx.crt) file into IOS.

I’m not savvy when it comes to software, so I was hoping to get some help on how to complete item 1 above. Specifically I don’t know how to create a new certificate with these specifications in a NextCloudPi docker instance.

Thank you for your help!