A short update:

By pure coincidence, I discovered a in data.zip/config file for a DELCO device these lines:

[tmc]
source="amaryllodyn"
internal_tmc_name="amaryllodyn"
port="COM,4"
update_ltn_on_country_change=1
tuner_model= "IGO_GPSTMC_TUNER"
tuneralg_rds_repeat_check=0
tmc_provider_name_use_old=1
tmc_provider_name=0
tuneralg_rds_packet_timeout=4500
tuneralg_8a_packet_timeout=8500
tuneralg_3a_packet_timeout=20000
tuneralg_last_8a_packet_timeout=60000
amaryllodyn_use_rds_input=0
auto_band_search_up=1
default_tmc_freq=892
check_ltn_support=1
area_size=500
use_picode_for_country_code=0
amaryllodyn_white_filter_state=1

I think it is worth adding them to sys.txt and try.