When the first rainbow screen disappears after first powering on, you should get a Raspberry logo in the middle of the screen. Under it is a message that says something like "Press SHIFT for recovery". When you see the Raspberry logo, Repeatedly press the Shift key until you get the NOOBS recovery menu. If you do nothing, then it will boot into the last chosen OS.
I'm able to see no screen showing no message, just the rainbow for a few seconds and then it's going to Lakka.
Have you only installed Lakka? If you had installed multiple OSes, then you would be presented with a list of OSes to boot from. But as you are not getting this menu, it sounds like you have only installed one OS.
No, in the same SD I have Raspbian and LibreELEC along with Lakka (let's call this SD_1), it's very weird just one day it stops showing the OS menu. I have others SD cards, I try to install noobs in a new fresh installation and I'm ending with the same result (SD_2), in (SD_3) I have installed only Rasbian using the image Rasberry application and it's working fine, the only difference between SD_1 and SD_3 is the time showing the rainbow screen, in the SD_3 with Raspbian only its shows for a very short time going to Raspbian very fast, Question: it's possible that the menu it's just not showing but working somehow?
If you want to install more than one OS, you must do them at the same time, otherwise you have to wipe your card and start again.
Yes, I believe its what I did for this SD_1; format--> download noobs_lite--> install following the instructions---> run, after that I was able to see the menu and download and install the other OS.
Let me try with PINN let me see how it goes.
Thanks for all your help.