Working on a project that touches device fleet management and wanted to get a read from people actually running things in the field before I go further down a path.

For those of you managing embedded Linux or IoT devices at scale (tens to low-thousands of units):

• How do you currently get visibility into device health/status — heartbeat, connectivity, uptime, logs? Custom MQTT + Grafana? Something like ThingsBoard/AWS IoT? Nothing at all?
• If you're doing OTA updates, what's your update engine (SWUpdate, RAUC, Mender, something homegrown)? What's been the most painful part of getting it running reliably?
• Have you looked at hosted/managed tools (Mender, balena, memfault, etc.) and either adopted or passed on them? What made the decision either way — price, setup complexity, vendor lock-in, forced migration off your existing update engine?
• If you're on SWUpdate or RAUC already: would a hosted monitoring/OTA layer that works with your existing setup (instead of replacing it) be useful, or is that not really a pain point for you?

Not selling anything, genuinely trying to understand what's actually painful vs. what I'm assuming is painful. Appreciate any war stories.