The bug with server & address that causes SEGV in dnsmasq is fixed post-2.86, here upstream:
https://thekelleys.org.uk/gitweb/?p=dnsmasq.git;a=commit;h=de372d6914ae20a1f9997815f258efbf3b14c39b
So maybe good to try this all again once 2.87 is ready.