W11 settings wouldn't allow svg association with Paint.net, seems to be hard wired on MS Edge. That can be changed to another app in the suggested list, Paint.net not being one of them, unfortunately. Setting the default for svg for a MS store app won't work as mentioned
If getting it on the suggested list is possible, great, otherwise attempting to find (the store) app on PC gets us to Where Is Paint.net, which isn't desirable either.