Install of ubuntu 20.10 fails to boot

Default install of Ubuntu fails to boot ("No boot disk has been detected or the disk has failed"). I tried different hard drives to be sure.

"Boot device: UEFI : Kingston... " shows up in my Bios start device selector, but it does not start.

I used "boot-repair" to try to fix the boot, but it fails too.

Boot-repair diagnostic (https://paste.ubuntu.com/p/mjYJjshHzb/) mentions "Please disable BIOS-compatibility/CSM/Legacy mode in your UEFI firmware" but I don't have this option on my firmware.

I can boot on the "live install" hard-drive, but all my other attempts at installing ubuntu have failed to boot on this 10 years old PC (Intel Atom CPU D2700 with 4GB RAM).

Any suggestion / help is very welcomed !

  sudo lshw -c storage -c disk
  *-usb:0                   
       description: Mass storage device
       product: JMicron
       vendor: JMicron
       physical id: 4
       bus info: usb@1:4
       logical name: scsi4
       version: 1.00
       serial: DB98765432125
       capabilities: usb-2.10 scsi
       configuration: driver=uas maxpower=30mA speed=480Mbit/s
     *-disk
          description: SCSI Disk
          vendor: JMicron
          physical id: 0.0.0
          bus info: scsi@4:0.0.0
          logical name: /dev/sdb
          version: 4102
          serial: DB98765432125
          size: 111GiB (120GB)
          capabilities: partitioned partitioned:dos
          configuration: ansiversion=6 logicalsectorsize=512 sectorsize=4096 signature=e30e38e0
  *-usb:1
       description: Mass storage device
       product: USB2.0-CRW
       vendor: Generic
       physical id: 7
       bus info: usb@1:7
       logical name: scsi5
       version: 38.82
       serial: 20090516388200000
       capabilities: usb-2.00 scsi emulated scsi-host
       configuration: driver=ums-realtek maxpower=500mA speed=480Mbit/s
     *-disk
          description: SCSI Disk
          product: Multi-Card
          vendor: Generic-
          physical id: 0.0.0
          bus info: scsi@5:0.0.0
          logical name: /dev/sdc
          version: 1.00
          capabilities: removable
          configuration: logicalsectorsize=512 sectorsize=512
        *-medium
             physical id: 0
             logical name: /dev/sdc
  *-sata
       description: SATA controller
       product: NM10/ICH7 Family SATA Controller [AHCI mode]
       vendor: Intel Corporation
       physical id: 1f.2
       bus info: pci@0000:00:1f.2
       logical name: scsi0
       version: 02
       width: 32 bits
       clock: 66MHz
       capabilities: sata msi pm ahci_1.0 bus_master cap_list emulated
       configuration: driver=ahci latency=0
       resources: irq:28 ioport:f0f0(size=8) ioport:f0e0(size=4) ioport:f0d0(size=8) ioport:f0c0(size=4) ioport:f020(size=16) memory:dff04000-dff043ff
     *-disk
          description: ATA Disk
          product: KINGSTON SA400S3
          physical id: 0.0.0
          bus info: scsi@0:0.0.0
          logical name: /dev/sda
          version: 0105
          serial: 50026B73810F6E1A
          size: 223GiB (240GB)
          capabilities: gpt-1.00 partitioned partitioned:gpt
          configuration: ansiversion=5 guid=6aa5e5f0-fd66-44d1-8175-caa6ee8acd05 logicalsectorsize=512 sectorsize=512