I installed Lubuntu dual boot with pre-existing Windows 11. I allocated a 400 MiB FAT32 /boot/efi partition, a root partition and a /home partition. Installation went smoothly. After reboot, there was no GRUB bootloader menu. The laptop loaded straight to Windows 11. The Boot tab in BIOS only showed Windows Boot Manager.
What I tried:
I installed dual-boot on a Dell Precision Tower 5810 (2017). Booted in both Lubuntu 24.04 LTS and Windows 11 like a charm.
Every Acer we have seen needs the “trust” setting on the ubuntu entry in UEFI.
You have to enable a password in UEFI, and never, ever lose that password or reset to blank when done, if not using UEFI Secure Boot.
In UEFI settings to get to trust setting. CtrlS
Acer Aspire S13 shows UEFI screen with trust setting
Thank you for your suggestions. Like you suggested, my ACER laptop requires a password to unlock configuration of UEFI Secure Boot.
After setting up the password, I took some liberty to inspect the Boot options. It has “Erase all Secure Boot Setting”, “Restore Secure Boot to Factory Default” and “Select an UEFI file as trusted for executing”. The last one gave me a directory tree:
You need to set “ubuntu” as trusted. Not sure if just the ubuntu folder or just shimx64.efi which is used for UEFI Secure boot. But shimx64.efi also works with Secure boot off. My system has never had Secure boot on and uses shimx64.efi.
Acer seems to accept Windows files as trusted so you should not have to do anything with them.
You need to either remember UEFI password forever, or reset to blank. You can either turn Secure boot off or maybe leave it on. It probably depends on if Secure boot was on or not when you installed. All the boot files with Secure Boot must be the signed copies, where unsigned versions are installed with Secure boot off.