I am also creating a Log viewer in a single HTML file (like Splunk, but a bit smaller). Pure JavaScript with no dependencies makes it runnable and integratable everywhere, which is nice.
Something you might be interested in is that journalctl (systemd's logger) can output real time logs in a format for server-sent-events (journalctl -o json-sse) so with a minimal bash http wrapper you can get realtime logs from most linux systems into your app.
https://github.com/dobin/SemiDataSieve