Just tried a native firefox-69.0.1 binary on NetBSD/amd64 9.0_BETA,
and so far the stability issues I had with the firefox NetBSD/amd64 8
binaries (on 8 & 9) seem to have completely gone.
I can consistently load maps.google.com, I no longer sometimes see odd
delays when fetching pages (including from localhost).
Colour me happy :-p