Their answer is listed below and keep in mind that links could get expired soon. According to their answer updates won't be officially validated and distributed through SM support download updates section. NO WARRANTY! If you're in doubt contact Supermicro Support directly for instructions.

Please try updating to firmware 4.07, linked below.
Be aware that this is not a validated firmware and this will likely not be officially validated due to the age of the platform. There is a small risk in flashing in general, since this board is out of warranty it's not impossible this will brick the BMC on the board (low chance but we have to warn).

This should address the expired certificate though, if you update then please let us know whether the issue is resolved for you, we are still gathering feedback.

https://box.supermicro.com/index.php/s/LE2wBZYrqrgKb35
Pass: Superm1cro!

Find SMCIPMItool through the link below.
https://box.supermicro.com/index.php/s/GTYpLFSfFA5qK4S
Pass: Superm1cro!

We're also aware the tools need an update and we have this available internally, the tools are also still being tested.
Could you try the version i linked below, it contains the updated versions of SMCIPMItool and IPMIview for both Windows and Linux.
https://box.supermicro.com/index.php/s/DGp3jgyPk29YL7x
Pass: Superm1cro!