Hey there.
Hope this help you.
Unlock MR200 V1 modem:
From openwrt console run adb shell
On modem console run:
uci set network_status.network_status_data.unlockPlmn=1
uci commit network_status
Reboot Mr200 (Power OFF/ON)
Tested on MR200(UN) 1.0 locked on Orange.
cat /etc/config/product
config product 'info'
option board_type 'mdm9225'
option product_type 'mr200-un-v1'
option product_id '02000001'
option product_id_ext '02000201'
option product_name 'MR200(UN) 1.0'
option hardware_ver '1.0'
option firmware_ver '1.0.0'
option firmware_ver_build 'Build 17/07/31 09:20:12 Rel.27n OFR'
option product_region 'UN'
option product_series 'MR200'
option vendor_name 'TP-LINK Technologies Co., Ltd.'
option ssid_prefix 'TP-LINK_LTE_MODULE_'