First up, I should say that that video you linked to is very good, I may bookmark that fellow, and see what other useful material he has. So thanks
The vid has also given you a headstart to some of the concepts I was going to mention. That includes the Something Else method of installing, to have control over your partitioning, the Windows ESP (EFI System Partition), and the Windows Disk Management utility.
I can put together a blow by blow plan for you, with a lot of text and a few screenshots, and I hope you can take it in, read it twice or more if necessary, and ask any questions. I will give you a general idea of what I will be suggesting next, and follow it with a few questions which, when answered by you, will enable me/us to help you better.
Broadly speaking, I will be suggesting that you
- Have a Windows Recovery Plan in place, so that you can restore your Windows if need be.
- If you still have a BalenaEtcher-driven USB stick that has one of the Ubuntu isos on it, use that to safeguard any information/data you created on the (once working) Ubuntu, by moving it from Point A to Point B.
- Use Windows Disk Management to blow away the existing two or more partitions containing the non-working Ubuntus.
Once that is done, you can look at
- Install your choice of the Ubuntus first, I would suggest Ubuntu Desktop, using Something Else and half the empty space allocated to it
- Reboot and see that it runs - it should generate a Grub Menu at start which features Ubuntu followed by Winows (listed as Windows Boot Manager), and then if that succeeds, in your Ubuntu
- Install Timeshift (it is in their Repositories, or else in your Software Centre), and take a snapshot
- Once that is effected, you can then look to install the other Ubuntu
You currently have an ESP which will be visible in your Windows Disk Management tool - it could be 100 MB, 300 MB, 500 MB, or even 1GB. It will be either FAT32 or perhaps vfat.
As the situation stands, it will contain a Folder for your Windows and one to two Folders for Ubuntu. We may need to tweak that.
So my questions at this point are
- Can you provide a screenshot from Windows Disk Management of the State of The Nation currently?
- What is the size/capacity of the SSD, and is it M2. or NVMe?
- Do you have any other drives, internal or external, besides the SSD?
There may be more questions, but if you can answer those 3 and be patient (I am in Australia), we can start with a good foundation.