Also look into the manual installation method laid out in GitLab. I will link when I get a chance!

PS C:\Users\Chris\Desktop\platform-tools_r30.0.0-windows\platform-tools>  ./fastboot reboot fastboot
Rebooting into fastboot                            OKAY [  0.005s]

But i run below command and get message:
PS C:\Users\Chris\Desktop\platform-tools_r30.0.0-windows\platform-tools> ./fastboot format:ext4 userdata
< waiting for any device >
and seems to waiting for device..

also tried to reboot to bootloader and i went to fastboot(without D)
tried to re run the installation and now the ubports stuck on Rebooting - Rebooting to fastbootD ,
on tablet is already on fastbootD

can i run the command: ./fastboot format:ext4 userdata on fastbood??

===========
UDPATE

I managed to complete the format:ext4:

PS C:\Users\Chris\Desktop\platform-tools_r30.0.0-windows\platform-tools> .\fastboot devices
HPV3M30P        fastboot
PS C:\Users\Chris\Desktop\platform-tools_r30.0.0-windows\platform-tools> ./fastboot format:ext4 userdata
mke2fs 1.45.4 (23-Sep-2019)
Creating filesystem with 13782267 4k blocks and 3448832 inodes
Filesystem UUID: ab7af7ba-06e4-11ef-9354-3174c3e6d4f0
Superblock backups stored on blocks:
        32768, 98304, 163840, 229376, 294912, 819200, 884736, 1605632, 2654208,
        4096000, 7962624, 11239424

Allocating group tables: done
Writing inode tables: done
Creating journal (65536 blocks): done
Writing superblocks and filesystem accounting information: done

Sending 'userdata' (316 KB)                        OKAY [  0.014s]
Writing 'userdata'                                 OKAY [  0.063s]
Finished. Total time: 0.328s
PS C:\Users\Chris\Desktop\platform-tools_r30.0.0-windows\platform-tools>  ./fastboot reboot fastboot
Rebooting into fastboot                            OKAY [  0.004s]
< waiting for any device >
fastboot: error: Failed to boot into userspace fastboot; one or more components might be unbootable.
PS C:\Users\Chris\Desktop\platform-tools_r30.0.0-windows\platform-tools>

Then I proceeded to follow the procedure exactly, entered the bootloader and launched ubports, which immediately recognized the tablet. I clicked continue on the ubports reminder to enter bootloader, and it automatically proceeded with the process. The tablet restarted, briefly entered the "recovery screen", and then reached fastbootD where it has been stuck for the past 5 minutes.
The current situation is that the tablet is in fastbootD and the ubports installer shows >Rebooting / Rebooting to fastbootD.

Every time it does this, I know that if I now press reboot to bootloader from the fastbootD menu it will proceed, but in ubports it will show an error.
Could it be due to the version of ubports, or the cable I'm using to connect to the type C port on the laptop?

The step before the step it errors requires fastbootd to format the user-data partition to EXT 4 which looks as though it is not happening.

Try this. Download the Platform tools version 30.0.0-6374843 from here. Extract it and in the extracted folder open a terminal.

Boot the tablet to fastboot.

Attach it to the PC and in the terminal run the command exactly as ./fastboot reboot fastboot

Leave the tablet alone until it reboots into fastbootd. This takes some time and the screen will look similar to the recovery screen (unfortunately I neglected to take a pic of that screen). If this screen appears fastbootd is working on your Windows PC.

I would try, I don't know if you would want to, but while in fastbootd run the command in the terminal:

./fastboot format:ext4 userdata

Then I would reboot the tablet to the bootloader (or fastboot without the d) and run the installer again, you would probably have to select the tablet from the drop down box.

I won't take responsibility for the device soft-bricking if it goes wrong (I have tried this method on the 2Gb version of the tablet and recovered it), however it is recoverable using the Lenovo Rescue and Smart Assistant tool.

I am encountering a problem with the installation, even though I have exactly the compatible model:
Tab M10 HD Wifi X306F 64GB / 4GB RAM - Android 11

The installation was done on Windows 10 64bit. I successfully unlocked the bootloader by following these steps:
https://whatmydevice.com/unlock/lenovo-tab-m10-hd-gen-2

Then I tried running the ubports-installer_0.10.0_win_x64 and chose the correct option: lenovo smart tab m10 hd 2nd gen wifi

I tried this process several times because sometimes ubports would say success and then during the installation on the tablet, the error I also have in the screenshot would appear, and other times an error appeared on ubports and I proceeded by pressing ignore. However, whenever I reached the installation, it would stop in the middle and the problem "no space left on device" would appear.
Please help me, I have this tablet and with the Stock ROM it is very slow, I see that I meet all the requirements to install ubuntu touch but I am not succeeding.

I flashed Android 11 onto it, which seemed to work, and then installed UT. Almost everything seems to work, although sometimes not fluently, but the sound is not working at all. I have to try with usb audio or bt audio. It might be that the audio hardware got upgraded for the Android 11 models and the drivers don't understand the old hardware. I would have to re-flash Android 11 to check if sound works on Android 11. It worked fine on Android 10.

I believe the installer should have warned me.

I believe you must have clicked through at least one warning before the installer tried to do as you asked it to.

TB-X306F 2Gb RAM and 32Gb Storage

OK, now I read this

My tablet is now bricked but not dead (it shows "Product: MT65xx Preloader"). Has anyone recovered it? I believe the installer should have warned me.

Thank you in advance