Try this...
lvextend -L +700G /dev/mapper/ubuntu--vg-ubuntu--lv
then run this...
resize2fs /dev/mapper/ubuntu--vg-ubuntu--lv
after this, do a df -h again to see how big your logical partition is now.
You can also do it in one command.
Code:
lvextend -L +700G /dev/mapper/ubuntu--vg-ubuntu--lv -r
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