There’s a huge amount variety between the alternative sbc providers, but I’m general:

• some are simply designed not to have various bits of hardware like the camera 22 pin connector.
• some fail to conform to the pis pin out or footprint, so hats won’t be compatible
• more commonly, documentation and support is so poor that extensive dev/Linux experience is required to get existing hardware to work

All of this makes it difficult to utilize alternatives without conducting considerable research into many different ones.