I did try the 2nd method and it still didn’t work. It still shows me the error about /dev/mapper/ubuntu–vg-root not found. Even though I checked the fstab file and everything seems configured properly. Now this is the guide I followed initially to setup the LVM on LUKS for Ubuntu
https://help.ubuntu.com/community/Full_Disk_Encryption_Howto_2019
As you can see from that guide it creates 2 LVM on LUKS one for root, home and all the rest and the other a LUKS1 for the encrypted boot. Now I don’t think this setup would work for Manjaro, so I thought of asking you, should I just scrap the existing LVMs on LUKS I have at the moment and just create 1 big partition for all the installation that is root, home, boot and everything else in just one big LVM on LUKS and then try to follow these guides again? As having two makes things so much more complicated and seems unnecessary as I think even if the boot partition is in a LUKS2 container it should still succeed in being decrypted at boot by GRUB.