"Please install all available updates for your release before upgrading."

You had replied #1 on this thread
https://trisquel.info/en/forum/how-install-trisquel-9-without-usb-drive-or-dvd
then #4 by loldier explains how one can upgrade to a new release, in your case from Trisquel 9 to 10, using the software updater. I think something like this is how I got from 8 to 9, the process took a long time is all I remember. If you can still access your installed Trisquel 9 maybe give this a try, see whether the software updater will point out that there is a new release, 10.

You may have seen the following script that was necessitated by some lack of certificates
at the mirrors from which we download trisquel software:
sudo sed -i s/http/https/ /etc/apt/sources.list which changes all the https's
in /etc/apt/sources.list to http's.

In desperation I modified that script to get an entirely different result:
sudo sed -i s/etiona/nabia/ /etc/apt/sources.list

Don't try this at home folks, we're all experts here ...

Changing:

deb https://mirror.math.princeton.edu/pub/trisquel-packages etiona main
deb-src https://mirror.math.princeton.edu/pub/trisquel-packages etiona main
deb https://mirror.math.princeton.edu/pub/trisquel-packages etiona-security main
deb-src https://mirror.math.princeton.edu/pub/trisquel-packages etiona-security main
deb https://mirror.math.princeton.edu/pub/trisquel-packages etiona-updates main
deb-src https://mirror.math.princeton.edu/pub/trisquel-packages etiona-updates main
#deb https://mirror.math.princeton.edu/pub/trisquel-packages etiona-backports main
#deb-src https://mirror.math.princeton.edu/pub/trisquel-packages etiona-backports main

To

deb https://mirror.math.princeton.edu/pub/trisquel-packages nabia main
deb-src https://mirror.math.princeton.edu/pub/trisquel-packages nabia main
deb https://mirror.math.princeton.edu/pub/trisquel-packages nabia-security main
deb-src https://mirror.math.princeton.edu/pub/trisquel-packages nabia-security main
deb https://mirror.math.princeton.edu/pub/trisquel-packages nabia-updates main
deb-src https://mirror.math.princeton.edu/pub/trisquel-packages nabia-updates main
#deb https://mirror.math.princeton.edu/pub/trisquel-packages nabia-backports main
#deb-src https://mirror.math.princeton.edu/pub/trisquel-packages nabia-backports main

Whereas the actual sources.list file for etiona looks like this:

deb https://archive.trisquel.info/trisquel/ etiona main
deb-src https://archive.trisquel.info/trisquel/ etiona main
deb https://archive.trisquel.info/trisquel/ etiona-security main
deb-src https://archive.trisquel.info/trisquel/ etiona-security main
deb https://archive.trisquel.info/trisquel/ etiona-updates main
deb-src https://archive.trisquel.info/trisquel/ etiona-updates main
#deb https://archive.trisquel.info/trisquel/ etiona-backports main
#deb-src https://archive.trisquel.info/trisquel/ etiona-backports main

Necessitating that the mirror site for the ensuing apt-get update and apt-get upgrade
be changed to suit.

This approach is bound to make a mess of nabia as the directory structures are not likely
to match between the two sets of software.

Unless there is a typo, I guess you need,

sudo sed -i 's/etiona/nabia/g' /etc/apt/sources.list

edit:
also, why not use:
do-release-upgrade