The LoRa devices, as well as others such as the RFM22B, allow for relativly rapid frequency shifts, so you can generate FSK RTTY fairly easily. Or FM tones (need access to DIO2) which if you have a suitable receiver, a handheld or SDR, is a quick and simple way of checking a LoRa device is working.
FSK RTTY is used for balloon tracking quite often in the UK, all you need is an el-cheapo SDR to receive it, the range is slightly less than LoRa at SF12.
Cant say I have ever seen the FSK data mode in a LoRa device used.
As for FSK RTTY on an LoRa\ESP32 combination I dont see why not, the delays would need to be set to get the baud rate correct, but thats a once only task.