I don’t know if it also happens to you, but I always have this fear (not only the equipment but also the whole freaking house).
I have two Synology NAS devices and one “custom” server (just a PSU, a Ryzen CPU, two RAM sticks and a SSD).
Everything is grounded, on a compliant safety electrical installation, but I don’t know… I’m maybe paranoiac by nature.
My biggest doubt is about the PSU. It is a certified PSU (from Be Quiet! IIRC), that has more than enough power (500W).
If you feel that your equipment is that questionable that it could catch fire at any moment, it’s time to replace your hardware.
Grab a can of compressed air and blow everything out once a year to reduce the risk of combustion. If you’re worried about things shorting out: do you have some questionable sata power splitters that need to be replaced? Anything like that you’ll replace all of them for $50, so just do it for peace of mind.
Don’t use the cheapest worst power supplies, use something that’s been reviewed and known to have working over-current protection which will cut the power should something go wrong.
And, as a last resort, find some kind of smart smoke sectors (or way to monitor audio/broadcast from smoke detectors) and a trust worthy smart power plug (with power monitoring) that you can connect all your gear to, so you can set up some automation to tell you if the alarm goes off, and either turn off the power automatically or have a way to remotely turn off the smart plug.
The smoke alarms we have, are 4 that communicate wirelessly between them, so they all go off together. Let Home Assistant monitor for that freq and you know if any smoke alarms go off.