I can't really. I used a Raspberry Pi 4 and later a 5, I used Canakits which provided approved power supplies for both, I used the highest-end SD cards I could get and then later used a special case/hat to instead use an NVME stick for storage. None of these were reliable.

I bet you could make a small book of all the times I've said this online and then had multiple people tell me "I'm running my whole life on a RPi v1, you're crazy, they are rock solid" (also people agreeing with me), I'm here to tell you I've spent literally hundreds of dollars following all the recommended guides and I've come to the conclusion that RPis are crap. I've owned every one of them from the original B-style one (I still have it) up to the 5th gen with the highest ram, I do not like them and I won't be buying them going forward.

> Is it the SD cards, or something else?

I have no clue, I'm sure it was the SD card at least one of the many times but it wasn't always something obvious. Sometimes the RPi would just lock up, no ssh, no ping, no web interface, and I'd have to power-cycle it to get it back up. I got tired of doing that and finally bought a BeeLink and it's been smooth sailing since then.