GRUB - Qubes alongside other Linux

Hello,

I have other Linux operation system which I want to use + the GRUB from that installation
I want to keep MX GRUB, and be able to load QUBES which Is installed on dedicated partition

before installation
|nvmeon1p1||ext4|1024|MiB|boot|
|nvmeon1p2||luks|24.4|GiB|MX|
|nvmeon1p3||swap|10|GiB|SwapMX|
|nvmeon1p4
||nvmeon1p5|luks|128|GiB|Qubes|
||nvmeon1p6|luks|313.54||HomeMX|

After installation
|nvmeon1p1||ext4|1024|MiB|boot|
|nvmeon1p2||luks|24.4|GiB|MX|
|nvmeon1p3||swap|10|GiB|SwapMX|
|nvmeon1p4|
||nvmeon1p5|luks|313.54||HomeMX|
||nvmeon1p6|luks|1|GiB|boot|
||nvmeon1p7|luks|127|GiB|Qubes|

I used ‘automatic’ installation, and choose which partition I want to preserve, and on which one system supposed to be installed.

Before automatic installation happened, I used custom installation option, but without success. Message that I saw was following.

You have not defined a root partition (/), which is required for installation of Qubes OS to continue.
You have not created a bootable partition

|How to install Qubes, so MX is installed, Grub from MX is installed, and I have option to choose between MX and Qubes?

Many Thanks