SVG files created with Inkscape cannot be uploaded: The namespace "http://www.inkscape.org/namespaces/inkscape" is not allowed

Yes, that is intended behavior and is a security feature, see Security Release – 3.5.4

You can, however, add additional allowed attributes, see How to define my allowlist for SVG attributes? (K3.6, Sane class) - #3 by lukasbestle