Hello. I want to install an SSD in PCIe but the system does not see it. I see the following in the kernel logs. Do I have a bad board? Can I configure it? I tried different firmware builds from 24.10 to the last snapshot.
The M.2 socket comes in several flavours (keyings), the OpenWrt One is M.2 M-key, offering a PCIe v2 x1 lane for SSDs (or other PCIe devices).
Your Transcend TS1TMTS425S SSD is a B+M-key SATA3 disk, it physically fits into an M-key M.2 slot, but only supported SATA3 - while the OO's M.2 M-key slots does not (and only does PCIe).
tl;dr: your SATA3 SSD does not/ cannot work in the OpenWrt One, you need an M.2 M-key PCIe (often called NVMe) SSD instead (the PCIe version doesn't really matter, but PCIe v3 and PCIe v4 SSD are common and will work just fine). The important part is that it is explicitly marked as something like "PCIe Gen4 x4" (or Gen3, Gen5, …) on the label.
According to https://transcend-info.com/product/internal-ssd/mte410s that should be a "PCIe Gen 4x4" M.2 SSD (and the picture confirms M-key), meaning it should work. Sadly the vendor doesn't really -obviously- mark the capabilities/ interface on the label, most other vendors are a bit more explicit and helpful there, e.g.: