[Xiaomi Poco F1 Questions & Answers] Heronicola:
My LTE Band Preference #65633 (in "Subscription ID: 0" where my SIM card is) reads 0x0000FFFFFFDF3FFF which when interpreted in QXDM notation would mean bands 1,2,3,4,5,6,7,8,9,10,11,12,13,14,17,18,19,20,21,23,24,25,26,27,28,29,30,31,32,33,34,35,36,37,38,39,40,41,42,43,44,45,46,47,48. I have no idea what this represents, and my bands in Network Signal Guru are the same as usual - 1,3,5,7,8,20,38,40,41.

And when I check the LTE Band Preference variable on Subscription ID: 1 (where my SIM card is not present), I get the message: "NV Status Error Received: Command Unrecognized."

I was also looking around the policyman directory in the EFS partition and found that the device_config.xml and post.xml files seem to contain radio configurations. I attempted modifying them and used this carrier_policy.xml from a Nexus 5X as an example https://gist.github.com/mccob/d998b066eb797154bf0e#file-carrier_policy-xml-L203

These is my modified carrier_policy.xml

<?xml version="1.0" encoding="UTF-8"?>

<!-- 7+7 mode Device configuration file for open Market DSDS with L+L support
$Header: //commercial/MPSS.AT.4.0.c2.6/Main/modem_proc/mmcp/policyman/configurations/DevConfig/7+7_mode/L+L/device_config.xml#1 $
-->
<policy name = "generic"
changelist = "$Change: 15210292 $"
policy_ver = "2036.1.6"
>

<initial>
<actions>

<rf_band_list name="rfbands">
<gw_bands base="hardware" />
<lte_bands base="none">
<include>1 2 3 4 5 7 8 12 13 17 20 25 26 38 40 41</include>
</lte_bands>
<tds_bands base="hardware" />
</rf_band_list>

<device_configuration num_sims="2" max_active_voice="1" max_active_data="2">
<config primary="C H G W L T" secondary="G W L T" />
<config primary="G W L T" secondary="C H G W L T" />
<e911_config primary="C H G W L T" secondary="G W L T" />
<e911_config primary="G W L T" secondary="C H G W L T" />
</device_configuration>

<feature subs="this"> dualmmode </feature>
<feature subs="other"> dualmmode </feature>

<ims_config allowed="true" subs="this" />
<ims_config allowed="true" subs="other" />

<rat_capability base="config" />
<rf_bands_if list="rfbands" />

</actions>
</initial>

<actions>
<rf_bands list="rfbands" />
<svc_mode>full</svc_mode>
</actions>
</policy>

and modified post.xml

<?xml version="1.0" encoding="UTF-8"?>

<!-- Post Policy for US location
$Header: //commercial/MPSS.AT.4.0.c2.6/Main/modem_proc/mmcp/policyman/configurations/Carrier/GenericUSA/post.xml#1 $
-->
<policy name = "generic"
changelist = "$Change: 15210292 $"
policy_ver = "1101.2.1"
>

<initial>

<mcc_list name="post:us_mccs" ns="global"> 310 311 312 </mcc_list>

<rf_band_list ns="global" name="post:fcc_compliant_bands">
<gw_bands base="hardware" />
<lte_bands base="none">
<include>1 2 3 4 5 7 8 12 13 17 20 25 26 38 40 41</include>
</lte_bands>
<tds_bands base="hardware" />
</rf_band_list>

<rf_band_list ns="global" name="post:default_bands">
<gw_bands base="hardware" />
<lte_bands base="none">
<include>1 2 3 4 5 7 8 12 13 17 20 25 26 38 40 41</include>
</lte_bands>
<tds_bands base="hardware" />
</rf_band_list>

<define_fullrat_config is_post="true">
<rf_bands list="post:default_bands" />
</define_fullrat_config>

</initial>

<if>
<any_of>
<not> <phone_operating_mode> ONLINE </phone_operating_mode> </not>
<not> <have_location /> </not>
</any_of>
<then>
<stop />
</then>
</if>

<svc_mode> FULL </svc_mode>

<if>
<location_mcc_in list="post:us_mccs" />
<then>
<rf_bands list="post:fcc_compliant_bands" />
</then>
<else>
<rf_bands list="post:default_bands" />
</else>
</if>

</policy>

I do not have the originals right now since I would need to reflash my stock EFS backup in order to read them.

This modification did not change band recognition. My Network Signal Guru only recognizes the original bands.

---------- Post added at 02:52 AM ---------- Previous post was at 02:39 AM ----------

For some further information, I am currently using a Project Fi SIM card which would allow me to access the T-Mobile, Sprint, and US-Cellular networks. I popped this in from my Nexus 5X which could connect to said networks without an issue. In the Pocophone F1, I am currently only able to use T-Mobile on the bands currently enabled, which would give me HSPA+ at the fastest.

In EFS Explorer at the bottom right there is a version number which reads, "AT4.0.c2.6-144-0710_2116_03" which is in common with the "MPSS.AT.4.0.c2.6" present in the headers of the post.xml and device_config.xml files in policyman.

From what I have searched, this is a Baseband firmware version which is also found on the OnePlus 6 and Xiaomi Mi MIX 2S which share the same SDM845. (And presumably there are even more devices with the same chipsets that share this baseband firmware)

This may mean that we could use these other devices' firmwares and EFS partitions to help us determine whats up with this device.