If I run hledger-web --serve --host 0.0.0.0 on my Raspberry Pi to expose web-hledger on all interfaces (in my case WiFi and VPN), some things break:

Most notably, opening 192.168.1.<Pi>:5000 redirects to 0.0.0.0:5000/journal.
Navigating to the journal directly does not help, since it still tries to load additional resources from 0.0.0.0 - the browser console is flooded with Failed to load resource: net::ERR_CONNECTION_REFUSED 0.0.0.0:5000/<resource>.