NFSv3 (udp, stateless) was always as reliable as the network infra under Linux, I found. NFSv4 made things a bit more complicated.
You don't want any NAT / stateful connection tracking in the network path (anything that could hiccup and forget), and wired connections only for permanent storage mounts, of course.
Obsidian.md has mobile versions, apparently. Whether there is a free sync feature for the ios version will be a Q.