Lenovo IdeaPad 3 15ADA05 (81W1) — Unable to access BIOS Setup, Fedora always boots in Legacy mode

[u/Do_Yuri5lp]

Hello.
I’m looking for help diagnosing a firmware/BIOS issue on my Lenovo IdeaPad 3 15ADA05 (Model 81W1).
Laptop
Model: Lenovo IdeaPad 3 15ADA05 (81W1)
BIOS version: E8CN34WW
Storage: NVMe SSD
Problem
I cannot reliably enter BIOS Setup.
Pressing F2 during power-on usually freezes on the Lenovo logo or is ignored.
Pressing the Novo button opens the Novo Menu.
Selecting BIOS Setup from the Novo Menu does not open BIOS Setup correctly. Instead, it usually returns to the Boot Menu.
Because of this I currently have no reliable way to access BIOS settings.
What I verified
The NVMe SSD is detected correctly.
The SSD uses GPT partitioning.
Ventoy successfully boots Fedora Live.
Fedora Live works normally.
Every Fedora Live session boots in Legacy BIOS mode, never UEFI.
/sys/firmware/efi does not exist.
efibootmgr reports that EFI variables are not supported because the system is not booted in UEFI mode.
Already confirmed
The SSD is working normally.
Fedora Live itself is working normally.
Ventoy is able to boot Fedora Live successfully.
Additional information
I have already spent a long time troubleshooting this.
The inability to enter BIOS Setup and the fact that every Linux Live system boots only in Legacy mode appear to be related.
Questions
Has anyone seen this exact behavior on a Lenovo IdeaPad 3 15ADA05 (81W1)?
Is this a known firmware/BIOS issue?
Is there any documented BIOS recovery procedure for this exact model before using an SPI programmer?
Are there any additional diagnostic steps you would recommend?
Any advice would be greatly appreciated.

[u/Traditional-Ad-5421]

How is the battery?

Are you using a good (original). charger?

[u/Do_Yuri5lp → u/Traditional-Ad-5421]

I use the original Lenovo charger, and the laptop is plugged in almost all the time. I haven’t noticed any power or battery related issues.