The HP P410 cards are very common and cheap.
My DL380 has the P410 on the mainboard... I only use it to boot the OS.
I use an LSI HBA + expanders for the data disks.
The H220 would be the cleaner solution of course.. but your disks might need a reformat, not sure.
Can't see why it wouldn't work with the ARC-1224.
Connecting with 2 SAS cables can enhance (not double) the max performance.
The linux update procedure could work with your controller.
These HP expanders are very reliable, but not very fast (3Gbps limit).
You might also want to check the forum...
If the expander is connected to your P410 then you can use the HP update tools... otherwise it's the linux procedure.
And yes, 2.10 is the last firmware.
Norco and Supermicro cases are the most popular I think.
If you use such big drives (8TB+), make sure to have enough parity.. (double disk failure during the long rebuild)
You might want to try the P20 driver here...
https://www.broadcom.com/products/storage/host-bus-adapters/sas-9210-8i
download - dirver - LSImpt_SAS_Windows_8.1_Windows_server_2012_R2_P20
I've been un-casing many usb disks recently. Some partitions were readable, most were not. Sometimes disk management wasn't able to delete the volumes, had to clean them with diskpart.exe first.