I'm using @mj82 patches and I was able to make a build for the venom by moving some packages from the kernel to kmod modules, this also may work for the mamba.
openwrt-mvebu$ git diff
diff --git a/target/linux/mvebu/config-5.10 b/target/linux/mvebu/config-5.10
index 1e31d8008a..dc4983659b 100644
--- a/target/linux/mvebu/config-5.10
+++ b/target/linux/mvebu/config-5.10
@@ -1,4 +1,3 @@
-CONFIG_AHCI_MVEBU=y
CONFIG_ALIGNMENT_TRAP=y
CONFIG_ARCH_32BIT_OFF_T=y
CONFIG_ARCH_HIBERNATION_POSSIBLE=y
@@ -46,15 +45,11 @@ CONFIG_ARM_THUMB=y
CONFIG_ARM_UNWIND=y
CONFIG_ARM_VIRT_EXT=y
CONFIG_ASYNC_TX_ENABLE_CHANNEL_SWITCH=y
-CONFIG_ATA=y
CONFIG_ATAGS=y
-CONFIG_ATA_LEDS=y
CONFIG_AUTO_ZRELADDR=y
CONFIG_BINFMT_FLAT_ARGVP_ENVP_ON_STACK=y
CONFIG_BLK_DEV_LOOP=y
-CONFIG_BLK_DEV_SD=y
CONFIG_BLK_MQ_PCI=y
-CONFIG_BLK_SCSI_REQUEST=y
CONFIG_BOUNCE=y
# CONFIG_CACHE_FEROCEON_L2 is not set
CONFIG_CACHE_L2X0=y
@@ -157,13 +152,10 @@ CONFIG_DTC=y
CONFIG_EARLY_PRINTK=y
CONFIG_EDAC_ATOMIC_SCRUB=y
CONFIG_EDAC_SUPPORT=y
-CONFIG_EXT4_FS=y
CONFIG_EXTCON=y
CONFIG_F2FS_FS=y
CONFIG_FIXED_PHY=y
CONFIG_FIX_EARLYCON_MEM=y
-CONFIG_FS_IOMAP=y
-CONFIG_FS_MBCACHE=y
CONFIG_FW_LOADER_PAGED_BUF=y
CONFIG_GENERIC_ALLOCATOR=y
CONFIG_GENERIC_ARCH_TOPOLOGY=y
@@ -206,7 +198,6 @@ CONFIG_HAS_DMA=y
CONFIG_HAS_IOMEM=y
CONFIG_HAS_IOPORT_MAP=y
CONFIG_HAVE_SMP=y
-# CONFIG_HAVE_ARM_ARCH_TIMER is not set
CONFIG_HIGHMEM=y
# CONFIG_HIGHPTE is not set
CONFIG_HOTPLUG_CPU=y
@@ -230,12 +221,10 @@ CONFIG_IRQ_DOMAIN_HIERARCHY=y
CONFIG_IRQ_FORCED_THREADING=y
CONFIG_IRQ_WORK=y
# CONFIG_IWMMXT is not set
-CONFIG_JBD2=y
CONFIG_LEDS_GPIO=y
# CONFIG_LEDS_LP50XX is not set
CONFIG_LEDS_PCA963X=y
CONFIG_LEDS_TLC591XX=y
-CONFIG_LEDS_TRIGGER_DISK=y
# CONFIG_LEDS_TURRIS_OMNIA is not set
CONFIG_LIBFDT=y
CONFIG_LLD_VERSION=0
@@ -376,12 +365,6 @@ CONFIG_RTC_DRV_MV=y
CONFIG_RTC_I2C_AND_SPI=y
CONFIG_RTC_MC146818_LIB=y
CONFIG_RWSEM_SPIN_ON_OWNER=y
-CONFIG_SATA_AHCI_PLATFORM=y
-CONFIG_SATA_HOST=y
-CONFIG_SATA_MV=y
-CONFIG_SATA_PMP=y
-CONFIG_SCSI=y
-# CONFIG_SENSORS_DRIVETEMP is not set
# CONFIG_SENSORS_MR75203 is not set
CONFIG_SENSORS_PWM_FAN=y
CONFIG_SENSORS_TMP421=y
@@ -393,7 +376,6 @@ CONFIG_SERIAL_MVEBU_CONSOLE=y
CONFIG_SERIAL_MVEBU_UART=y
CONFIG_SFP=y
CONFIG_SGL_ALLOC=y
-CONFIG_SG_POOL=y
CONFIG_SMP=y
CONFIG_SMP_ON_UP=y
CONFIG_SOC_BUS=y
@@ -434,7 +416,6 @@ CONFIG_USB_EHCI_HCD_ORION=y
CONFIG_USB_EHCI_HCD_PLATFORM=y
CONFIG_USB_LEDS_TRIGGER_USBPORT=y
CONFIG_USB_PHY=y
-CONFIG_USB_STORAGE=y
CONFIG_USB_SUPPORT=y
CONFIG_USB_XHCI_HCD=y
CONFIG_USB_XHCI_MVEBU=y
diff --git a/target/linux/mvebu/image/cortexa9.mk b/target/linux/mvebu/image/cortexa9.mk
index ea20a25a29..3bf53c29a9 100644
--- a/target/linux/mvebu/image/cortexa9.mk
+++ b/target/linux/mvebu/image/cortexa9.mk
@@ -156,7 +156,7 @@ define Device/linksys_wrt32x
DEVICE_ALT0_VENDOR := Linksys
DEVICE_ALT0_MODEL := Venom
DEVICE_DTS := armada-385-linksys-venom
- DEVICE_PACKAGES += kmod-btmrvl kmod-mwifiex-sdio mwlwifi-firmware-88w8964
+ DEVICE_PACKAGES += kmod-ata-ahci kmod-ata-core kmod-ata-marvell-sata kmod-scsi-core kmod-scsi-generic kmod-usb2 kmod-btmrvl kmod-mwifiex-sdio mwlwifi-firmware-88w8964
KERNEL_SIZE := 3072k
KERNEL := kernel-bin | append-dtb
SUPPORTED_DEVICES += armada-385-linksys-venom linksys,venom
(END)
Image Name: ARM OpenWrt Linux-5.10-rc7
Created: Tue Dec 8 23:03:06 2020
Image Type: ARM Linux Kernel Image (uncompressed)
Data Size: 2965821 Bytes = 2896.31 KiB = 2.83 MiB
Load Address: 00008000
Entry Point: 00008000