How can i install OpenBSD alongside endless?

english install
,
1

How many partitions i should create if i want to dualboot this system’s

2

https://support.endlessm.com/hc/en-us/articles/210527003-Can-I-install-Endless-alongside-an-existing-operating-system-like-Windows-or-OSX-

3

No. I want to install OpenBSD from endless, not endless from OpenBSD

4

Endless OS only supports dual-boot with Windows