I saw two pictures on the ask ubuntu post; but I didn’t see any error message sorry when I looked earlier.
I’ve looked again and I can see what I think has you confused; mention of an EFI (ESP or EFI system partition) partition.
You haven’t provided any details about your box; if it’s a legacy or BIOS box - no ESP partition is required; however if it’s uEFI then yes it is required.
Your partition layout appears to be
/sda1 ext4 - this is likely your old system (~116GB)
/sda3 *unknown* thus ??? (116GB)
/sda2 extended (logical partition entry only)
/sda3 utilizing the space of sda2 swap of 900MB
I have no idea what sda3 is as you’ve provided no details.
sda1 appears to be where your old Ubuntu system was.
I’d remove sda2+3 as I see no point in having an extended partition of that small size. Personally I’d create a larger swap file (I’d make it >3GB at least; it needs to be larger than RAM size to hibernate, but size is a very subjective thing based on how you’ll use the box). I’d suggest not creating a swap partition, but use a swapfile instead following instructions as written by @leokhere.
If you need to create an EFI/ESP partition you can then use the space made available by the deletion of the swap partition, for creating a EFI partition. It needs to be fat32 and a size of 300MB should be good.
I’ll provide a link which may better represent your issue (now what I see what I think has thrown you), try looking at
Note: If your box is BIOS (ie. decade+ old, or XP/Vista era box), the system will boot even with that error message. If your box is uEFI (win8/10) then the error message needs to be followed (as it likely won’t boot without it).
(FYI: If you noted I missed win7 it’ll most boot without EFI partition, but a late win7 box may require uEFI or ESP partition)
You’re using EFI as @apt-ghetto correctly highlighted (what I missed in your picture) so use the steps & link I provided for that install (ie. I provided another askubuntu link where I walked through what I do for a lubuntu install on a then groovy system on a uEFI only box)
(if I re-did that on today’s QA-test install with impish, I can’t imagine anything would differ over the word groovy being replaced by impish. I covered the size; 300MB is enough generally for normal end-users; but I often put many installs on test boxes (more so than end-users do) thus the larger size I mentioned in that question).
On that last screen you’re on where the window reads “Create a Partition”, you will need to do this at least twice—one for ESP and one for /.
You need at least an ESP partition which has been mentioned above and you need a partition for Lubuntu to install itself to.
If you’re being thrown off by what’s being shown on the AskUbuntu answer, please note that the image shown there is showing what you might see when creating a partition for /. You need to create a smaller partition (probably 300Mb as recommended) for your ESP in addition to the system partition for /.
Please review the answer again and walk through the steps. The ESP will be a primary partition with a fat32 file system with the mount point being /boot/efi. Also, you need to set the correct flags in order to boot.
After creating the ESP, you can create your partition for /. As it was mentioned, you don’t need to create additional partitions after the system partition if you aren’t comfortable with it (more advanced). Lubuntu should boot just fine with those in place provided you followed the guide correctly.
If you’re ok with just having those 2 partitions for your install, you can just let the system partition for / take up the total remaining free space on your disk after creating your ESP. Good luck.