Syncronize subscribed calendar to email client and mobile devices

I subscribed to many subscription calendars in my mailbox.org calendar account.

However, as of now, subscription calendars are not synchronized from my mailbox.org account to my devices:

• Thunderbird using TbSync on MacOS and Fedora (Linux)
• GNOME Calendar on Fedora (Linux)
  
• iPhone accounts (iOS)

When adding one subscription calendar, it requires a lot of manual labor for each individual device.

Please implement the feature that subscription calendars are synchronized from my mailbox.org account to all my devices?