>only source of unreliability I have experienced

Consider yourself lucky then.

Tried that then discovered there is a Pi/UASP incompatibility with the USB adapter I bought. So need to disable that murdering what little speed the USB contraption had.

And then the power supply isn't sufficient anymore so buy a different one. Only to discover it was actually the cable not the supply. Then you start to investigate SSD power draw realize wait how does that even work USB can't provide that much. Only to learn that USB attached SSDs run in low power mode. Not that it matters cause it's USB throughput constrained anyway and adapters don't use x4 lanes on the nvme.

I do have multiple rasps set up like that, but I consider it mistakes learned the hard way rather than a desirable setup.

Hmm. I currently have a HDD and SSD attached to the USB ports of a Raspberry Pi 4B. I leave in on 24/7 as a media streamer and a PiHole.

It does however have an Argon One PSU which is capable of supplying 3.5A.

I learned early on to not skimp on the PSU, and have mostly used official Raspberry Pi PSUs in order to avoid brownout unreliability.

Yeah they definitely have their uses. I've got a cluster of SBCs which is fun (mix of rasp4 & 32gb orange pis), but in hindsight I kinda wish I had spent the cash on one powerful device instead.