I recently heard about Sixfab (https://sixfab.com/), they mainly concentrate on rapsberry pi hats, don’t know if that would fit your need, but they offer a lot of information in their docs.
If you are not on a raspberry the Base HAT (https://sixfab.com/product/raspberry-pi-base-hat-3g-4g-lte-minipcie-cards/) can be used by micro USB instead of the GPIO pins (feature no. 7) and you can choose between different PCIe modules (https://sixfab.com/product-category/cellular-modems/) which is a nice feature in my opinion. Overall their solutions seem much more thought through to me but I haven’t used them so far.