Whilst I’m using the ATmega4808/9 (6KB/48KB) as I can get them and if a client needs it, I can make it talk Arduino, I’ve not got any issues with LMIC 4.1 which is LoRaWAN 1.0.3 fitting in to a Pro Mini (328) for a couple of sensors on I2C using OTAA, downlinks, ADR and all the trimmings.
Using an ATtiny with send only ABP was a compromise the day it was launched.