I always have to create the bootloader when I install solus on my Dell Inspiron. I use this to fix it everytime; https://www.reddit.com/r/SolusProject/comments/9iglk9/solus_entry_not_showing_up_on_uefi_boot_menu/e6jluua/
Just in case reddit goes away for some reason:
Install efibootmgr: sudo eopkg it efibootmgr
Run efibootmgr with no arguments. You should see an entry for Linux Boot Manager, which for some reason doesn't show up in your actual boot menu but does here. There's a number listed for that entry. Delete it with sudo efibootmgr -b [num] -B
Now you can recreate it. If your EFI partition is /dev/sda1 then do this: sudo efibootmgr -c -d /dev/sda -p 1 -l "\EFI\systemd\systemd-bootx64.efi" -L "Linux Boot Manager"
This can all be done from the live environment on your bootable media, that you used to install initially.
