I can't even begin to use the Seamless Pattern template. The moment I open it, Inkscape crashes. I've tried repeatedly and have even reinstalled Inkscape 1.1 twice.

Yesterday, before I tried the new Seamless Pattern template, I had installed my page size preferences as a template. Could this have anything to do with the failure above?

By the way, I never had any trouble with the Seamless Pattern extension in the version prior to 1.00. Was it too much trouble to migrate the extension to 1.00?

I'm not a programmer or professional artist, just an amateur but enthusiastic user.

I can confirm this behaviour on macOS - no way to establish this template. From the Chat: The author says he needs to work on the extension to update to a new API (application programming interface). No estimated date available from what I can tell.

Thanks, Polygon, for the information. Does that mean that Seamless Pattern will eventually go back to being an extension? Or will it remain a template?

I should have said I'm using Windows 10 64-bit.

I removed my user preferences template, uninstalled Inkscape, and reinstalled, and it didn't make any difference. I seem to be able to open the other templates with no problem.

I have no clue - other templates are not affected from my experience.

Here's a workflow to create your own seamless pattern without using the template. 

Draw a rectangle.  This is only used to set the size of your tiles and will be deleted later.  Create a single-member group from this rectangle, then [Edit > Clone > Create Tiled Clones...].  Use all the default settings with enough rows and columns to cover your work area.  (It occurs to me as I write this that changing the clone rotation and symmetry might produce some interesting effects.)

Now go back into the original group.  Anything you add will be seamlessly reproduced in the tiled clones.  Feel free to draw outside the box.  The group can grow or shrink without moving the tiled clones.  Lastly, delete that rectangle you started out with.  

And if you draw something you're happy with, show it off!

Hi,
In Inkscape 1.0.2 it starts without a problem, but is indeed listed as a template.
It is the same extension I think, but just in a different place in the menu.
Here it works with Windows 8.1, 64 bit.

I always have different versions of portable Inkscape installed next to each other on my pc.
Exactly for this kind of thing, where an extension doesn't work in the newer Inkscape.
After making it in 1.0.2, you can open the file in 1.1.

And yes, of course you can also craft a seamless pattern yourself like Paddy_cad describes. :-)
Please show us the results with rotation, Paddy!

Thanks very much, Paddy_CAD, for the workflow and for reminding me about the wonders of cloning.  I'll try out your process!

Kirstie, that's useful information about 1.0.2 working with Seamless Pattern.

By the way, I'm on Windows 10, 64-bit. I need to get in the habit of saying that.

I just noticed that the attachment is missing from #5 above.  Here it is.