After installing Solus OS in dual (in fact multi)-boot along Windows 10 and Kubuntu 20.04 the laptop shows at boot the boot menu created by Grub Customizer in Kubuntu (which I like) but without the last installed system (Solus). Updating grub doesn't add Solus, neither does any action in Grub Customizer.
I can add only an option called by default "UEFI Firmware Settings" which is a link to the BIOS Startup Menu. Solus can be booted there by selecting Boot Menu > UEFI Linux Boot Loader.
(That can be accessed with Esc
for BIOS Startup Menu, as said here).
But can Solus be added to the Kubuntu grub list - I mean from Kubuntu?