It looks like Bios can be updated using FreeDos 1.1:
For the record it is based on InteL FirmWare Update Utility version 6.0.0.1184
Note exe be run from win10 previously installed on usb disk but is not actually flashing, use FreeDos
Random notes:
*-core description: Motherboard product: 0XC7MM vendor: Dell Inc. physical id: 0 version: A00 serial: ..??????????????. *-firmware description: BIOS vendor: Dell Inc. physical id: 0 version: 2.4.0 date: 01/13/2011 size: 64KiB capacity: 2MiB capabilities: isa pci pnp apm upgrade shadowing escd cdboot bootselect socketedrom edd int13floppy1200 int13floppy720 int13floppy2880 int5printscreen int9keyboard int14serial int17printer int10video acpi usb ls120boot zipboot biosbootspecification
00:00.0 Host bridge: Intel Corporation Core Processor DMI (rev 11)
01:00.0 VGA compatible controller: Advanced Micro Devices, Inc. [AMD/ATI] RV730 GL [FirePro V3750] 02:00.0 Ethernet controller: Broadcom Inc. and subsidiaries NetLink BCM57780 Gigabit Ethernet PCIe (rev 01)
description: Mini Tower Computer product: OptiPlex 9020 (OptiPlex 9020)
http://www.fujitsu.com/downloads/EU/es/soporte/discosduros/guia_inst_MAN_MAM.pdf
usb boot bios
NMI watchdog: BUG: soft lockup - CPU#1 stuck for 22s! [systemd-timesyn:504]
0000:01:00.0 0300: 1002:5460 # [[ATI]]
00:02.0 VGA compatible controller [0300]: Intel Corporation Mobile 945GM/GMS/940GML Express Integrated Graphics Controller [8086:27a2] (rev 03) (prog-if 00 [VGA])