Hello, I ran into this same issue and found how to fix.
Apparently EV now stores the "template" as a new kind of note instead of previously, where you just used a blank note that you like as a template by making a new copy.
Once you download the templates from EV (the ones that show they are locked), you need to view the note and click the three dots in the upper right, then click save as template.
To use the template, start a new blank note and notice that there's now a little button to click called Template. (I'm using desktop version 18.104.22.16834)
When you click the Template button, the note you started now has the Template content and it is editable.
This doesn't explain how to make new templates like this, but I do like the approach.
With this new process, I don't have to worry about bashing my templates by forgetting to make a copy before using it.