You don’t actually need a special browser “plugin” on the Raspberry Pi to remote-control OBS — what matters is that obs-websocket (the server) is installed in the OBS host, and the Pi just runs a Web UI (Chrome/Firefox) that connects to that websocket.
If you’re trying to run obs-websocket on the Pi itself (i.e. OBS on the Pi), prebuilt .deb installers are usually amd64 only, so you’ll likely need to build obs-websocket from source for ARM: install build deps (cmake, build-essential, libobs dev headers), clone the repo, checkout the release tag and run a normal cmake/make/install flow.
For the front end (obs-tablet-remote or similar) on the Pi you’ll want a modern Node runtime — update Node (NodeSource or nvm) if the Pi’s distro ships an old version.
If you serve the UI over HTTPS and proxy to the OBS websocket, make sure nginx (or your proxy) forwards websocket headers (proxy_set_header Upgrade $http_upgrade; proxy_set_header Connection "upgrade"; proxy_http_version 1.1;) so the browser can establish a wss:// session.
The “security ok but browser won’t handle it” symptom is usually mixed-content or insecure ws:// from an https:// page — switch to wss:// or proxy/terminate TLS at nginx to fix it.
To run the Node UI reliably on a Pi, use PM2 or a simple systemd unit so it starts at boot and restarts on crashes.
If you want to avoid heavy Pi builds, the simplest approach is: run OBS + obs-websocket on your desktop (x86), and control it from the Pi browser over the LAN — no compiling, just configure firewall and websocket port.
Finally, if you need to compile on the Pi, double-check your OBS SDK/dev headers version matches the obs-websocket release you’re building — mismatched headers are a common source of build failures.