@wide-carpet-65149 the 40pin header on all RPis since a long time (starting with B+ iirc), so they should be pin compatible. However, please be aware of the power usage and possibility of non standard pin usage (you can mitigate that to some extent by reassigning pins via that python script for pin mapping) I would double check with the HAT board specs. Before trying anything.

@fierce-france-36958 that's a good point, I did not think about power requirements. Need to check that. I thought pins would either match always or be re-assignable. Thanks!

The pins will always match if hat & pi both have a 40 pin header (the older 26pin header can be matched by reassigning the 40pin header)

Ahh that makes sense, yes the HAT mentioned 40 pin connector. The HATs are INR 2K - 5K each, I need 3, so surely will double check. No need wasting money on this.

Multiple hat is tricky, only very few hats are stackable

In that case I can still get the TPlink USB LTE dongle, they are cheap. With RPi 4, should work well.

RPi is a good prototyping platform and for small scale deployments, you can make do with those provided power and packaging isn't too much of a constraint