Pop!_OS 20.04 Intel x86_64 Unencrypted installation doesn't install boot loader correctly

[luisnabais]

Distribution:
NAME="Pop!_OS"
VERSION="20.04 LTS"
ID=pop
ID_LIKE="ubuntu debian"
PRETTY_NAME="Pop!_OS 20.04 LTS"
VERSION_ID="20.04"
HOME_URL="https://system76.com/pop"
SUPPORT_URL="http://support.system76.com"
BUG_REPORT_URL="https://github.com/pop-os/pop/issues"
PRIVACY_POLICY_URL="https://system76.com/privacy"
VERSION_CODENAME=focal
UBUNTU_CODENAME=focal
LOGO=distributor-logo-pop-os

Issue/Bug Description:
If I install Pop!_OS 20.04 with disk encryption, the installation completes normally, but if I do the same installation, but select to not encrypt the disk, the computer says no OS is installed, so I think there is something related to the installer, which is causing boot loader not to be correctly installed.
It's an old Lenovo Yoga 500-14IBD, a 14" laptop, i5 5th generation with 8GB RAM and a normal 2.5" 256GB SSD and . No EFI, just regular BIOS.
I did the process with all partitions deleted, used the default option to make a clean installation.

Steps to reproduce (if you know):

1. I cleared every partitions, make sure only free space is shown in GParted.
2. Selected Clean Installation and Erase and Install.
3. Chose to not encrypt the disk, left everything else default.
4. Restart computer
5. With disk encrypted, I get the message to insert the encryption password, without encryption, I get a message to select which hard drive has the operating system.

Expected behavior:
Install normally, but without encrypted disk.

Other Notes:
I tried English and Portuguese installations, just to eliminate possibilities, like bugs related to encoding. Didn't make a difference.

ISO file: pop-os_20.04_amd64_intel_5.iso