This also happened to me, the GSM part disappeared.
The solution for two devices after this flawed update was.
Reinstall help PC - usb ubports-installer

Personally, the GPS works, but it is unreliable, wifi must not be turned off and sometimes the phone must be completely restarted.
then sometimes it takes minutes or tens of minutes for the GPS to find the location

I did a Reinstall without deleting user data and it stayed pretty much the same.
Tried wiping /cache and /tmp and it didn't help either

problem :
used by the system
they compare with other redmi note 7
used by the system much (many times larger)
How to clean??

problém : Používá systém, porovnávají se s jinými poznámkami redmi 7 používanými systémem mnohem (mnohokrát větší) Jak čistit??

I'm just guessing can you run the installation like on a PC or is it fully automatic?

From what did you install ?
directly https://ubuntu.com/download/server/arm ?

if so, then when installing Ubuntu in the step of selecting the disc you can set ( change ) the size of /

My problem with the gallery ( displays only black squares ) was solved by playing the new system installation over the usb cable
(20.04 )

Redmi note 7 . UB 20.04 ota-4
Problem losing voice during call.
tested has a connection with switched on cellular. data
if there is a data connection via wifi problem is not , emergency solution turn off cellular data during call. Then the call does not lose voice.

16.04 doesn't make me

Redmi note 7 ver 20.04 (OTA-4)
when plugging in the charging of the switched-off phone, the fasboot automatically activates

Personally, the GPS works, but it is unreliable, wifi must not be turned off and sometimes the phone must be completely restarted.
then sometimes it takes minutes or tens of minutes for the GPS to find the location

I would try a different USB port and a different connection cable