Support vector-effect for SVG elements. vector-effect: non-scaling-stroke would allow strokes to keep the same width as the SVG scales as a whole. https://www.w3.org/TR/SVGTiny12/painting.html#VectorEffectProperty
Amelia Bellamy-Royds commented
Updated spec link: https://www.w3.org/TR/SVG2/coords.html#VectorEffects
All other major browser rendering engines (Gecko, Chromium, WebKit) support the `non-scaling-stroke` value.
A tentative Firefox implementation of the additional values from SVG 2 is currently on hold, panding commitments to implement from other browsers. See this Firefox bug discussion: https://bugzilla.mozilla.org/show_bug.cgi?id=1318208
Chromium feature request is here: https://bugs.chromium.org/p/chromium/issues/detail?id=691398