Unlikely since the most ISM bands are UHF (EU is 868 MHz) and skywave propagation (what you’re referring to) is characteristic of HF radiation (3-30MHz). VHF/UHF radiation passes through the ionosphere instead of refracting.

Not at 900MHz. Skywave propagation mode is only available under about 30MHz. Above that, the signal reliably continues on into space.

At frequencies this high, you’re realistically limited to near line of sight paths.

Temperature Compensated Crystal Oscillators (TCXOs) is what they should be looking for. And to be clear you can get SX1262 variants with such, eg: https://wiki.seeedstudio.com/wio_sx1262/

For the detailed run down, see https://cdn.sparkfun.com/assets/f/f/b/4/2/SX1262_AN-Recommen... page 14

> In the case of an SX1262 operating at +22 dBm in the US 902 – 928 MHz band, the frequency drift measured during the maximum LoRAWAN™ packet duration stays below the maximum limit, provided thermal insulation is implemented around the crystal during PCB design.

> At extreme temperatures (below -20 °C and above 70 °C), it is recommended to use a TCXO.

> For any other frequency bands corresponding to longer RF packet transmissions at +22 dBm, it is recommended to use a TCXO.

You mean they don't have temperature compensated? What you described is temperature dependent

This is a radio module issue, not a chip issue.

Cheap modules have cheap crystals, better ones have a TCXO.