So, here is how I manage it, if the line height cannot be reduced sufficiently by the numeric entry/spinbox: Try clicking the question-mark (un-set variable inline height).If that does not resolve the issue, activate the Tt button ("outer" text style) and set the font height to something small and linespacing to something small and click the questionmark.Then de-activate Tt (outer) and edit the text normally.i.e. The outer style overrides the inner style.

watch out for those nonstandard Affinity SVGs. Their viewbox/scale is broken (and more)

Inkscape is professional, free, open source Vector Graphics software.

I'd also try opening the .svg file in Scribus and outputting to pdf from there. You've got more output settings, can handle bleed and add printers' marks etc.

The following might be a pretty cumbersome workaround for tiled clones with spacing e.g. in millimeters instead of %.