Two Ubuntu based distributoions not work correct

[Matej]

I installed first Lubuntu on one BTRFS partition, then I install Ubuntu desktop latest version on second BTRFS partition.
But Lubuntu is now hidden, without functional boot loader.

Exist any solution?

I tried a lot of solutions but it not helped me:
--Boot-Repair
--sudo update-grub
--efibootmgr
--rEFInd boot manager

My settings in my computer and in my SSD are:
--UEFI mode (not BIOS)
--GPT GUID Partition Table

I used manual partitioning:
--500 MB on vFAT /boot/efi
--500 MB ext4 /boot/
--25 GB BTRFS root for Lubuntu
--25 GB BTRFS root for Ubuntu

Thank you very much

[Matej]

I extremely hard work, a lot of days testing multi boot, multi Ubuntu based distros.
I can you provide you a lot of precious informations.
Ubuntu based distributions damage or remove data in EFI partition/folder, if I install second OS on the same disk. For example removed rEFInd boot manager from EFI too.
For example I installed first Lubuntu, then “KDE neon“ distro. KDE neon has in EFI folder name “neon” but Lubuntu data was damaged in EFI folder by KDE neon distro installation.