[ASUS ROG Phone II Questions & Answers] dennis96411:
I found something interesting. I listed the /bin directory and saw a "cmd" executable. Running it from ADB gave me this:

ASUS_I001_1:/ $ cmd -l
Currently running services:
DockObserver
MinkBinderSvc
SurfaceFlinger
accessibility
account
activity
alarm
android.os.UpdateEngineService
android.security.keystore
appops
appwidget
asus_game_mode
audio
auralight
autofill
backup
battery
batteryproperties
batterystats
binder_calls_stats
bluetooth_manager
carrier_config
clipboard
cneservice
com.qualcomm.location.izat.IzatService
commontime_management
companiondevice
connectivity
connmetrics
consumer_ir
content
contexthub
country_detector
cpuinfo
crossprofileapps
dbinfo
device_identifiers
device_policy
deviceidle
devicestoragemonitor
diskstats
display
dpmservice
dreams
drm.drmManager
dropbox
ethernet
extphone
fingerprint
gfxinfo
gpu
graphicsstats
hardware_properties
imms
input
input_method
iphonesubinfo
ipsec
isms
isub
jobscheduler
launcherapps
location
lock_settings
media.aaudio
media.audio_flinger
media.audio_policy
media.camera
media.camera.proxy
media.drm
media.extractor
media.metrics
media.player
media.resource_manager
media.sound_trigger_hw
media_projection
media_resource_monitor
media_router
media_session
meminfo
midi
miscsetup
mount
netd_listener
netpolicy
netstats
network_management
network_score
network_time_update_service
network_watchlist
nfc
notification
oem_lock
optiflex
otadexopt
overlay
package
package_native
permission
persistent_data_block
phone
pinner
power
print
processinfo
procstats
qti.ims.ext
recovery
restrictions
scheduling_policy
search
sec_key_att_app_id_provider
secure_element
sensorservice
serial
servicediscovery
settings
shortcut
simphonebook
sip
slice
soundtrigger
stats
statscompanion
statusbar
storaged
storaged_pri
storagestats
system_update
tcexternal
telecom
telephony.registry
textclassification
textservices
thermalservice
trust
uimode
updatelock
usagestats
usb
user
vendor.audio.vrservice
vendor.perfservice
vibrator
voiceinteraction
wallpaper
webviewupdate
wfdservice
wifi
wifiasus
wifiaware
wificond
wifip2p
wifirtt
wifiscanner
wigig
wigigp2p
window

I eventually got to this point:

ASUS_I001_1:/ $ cmd phone ims
IMS Commands:
ims set-ims-service [-s SLOT_ID] (-c | -d) PACKAGE_NAME
Sets the ImsService defined in PACKAGE_NAME to to be the bound
ImsService. Options are:
-s: the slot ID that the ImsService should be bound for. If no option
is specified, it will choose the default voice SIM slot.
-c: Override the ImsService defined in the carrier configuration.
-d: Override the ImsService defined in the device overlay.
ims get-ims-service [-s SLOT_ID] [-c | -d]
Gets the package name of the currently defined ImsService.
Options are:
-s: The SIM slot ID for the registered ImsService. If no option
is specified, it will choose the default voice SIM slot.
-c: The ImsService defined as the carrier configured ImsService.
-c: The ImsService defined as the device default ImsService.
ims enable [-s SLOT_ID]
enables IMS for the SIM slot specified, or for the default voice SIM slot
if none is specified.
ims disable [-s SLOT_ID]
disables IMS for the SIM slot specified, or for the default voice SIM
slot if none is specified.

ASUS_I001_1:/ $ cmd phone ims get-ims-service -c
com.google.android.ims
ASUS_I001_1:/ $ cmd phone ims get-ims-service -d
org.codeaurora.ims

Looks like it has something to do with this: https://android.googlesource.com/pl.../com/android/phone/TelephonyShellCommand.java