Filters, gradients don't work in linked SVGs

Summary:

Filters and gradients don't work with linked SVGs. I suspect Inkscape is failing to find <defs> in the linked SVG? (This unfortunately makes linked SVGs almost unusable.)

Steps to reproduce:

• Place all attached files (blur.svg, blur-test.svg) in the same directory.
• Open the attached blur-test.svg.

What happened?

The boxes are not blurred. The gradient is not visible. The curve is a B-spline.

What should have happened?

The boxes should be blurred. The gradient should be visible. The curve should be (and is) a B-spline, but that is explained by Inkscape baking the computed path into the SVG.

Sample attachments:

blur.svg blur-test.svg

Version Info:

- Inkscape Version: 1.0.2 (e86c870879, 2021-01-15)
- Inkscape Package: inkscape-1.0.2-1.fc33.x86_64
- Operating System: Fedora 33 (Linux)