I'm in contact with Areca and they tell me they have sent new driver to Apple which sadly they haven't included yet neither in the latest beta, Areca is now working on a temporary solution until it's supported.
I will be returning the M1, knowing Apple this could take months.
Here is the latest mail:
after some tests, i am afraid that we may not able to support M1 machine in current stage. the current problem is OS11 force load the buildin driver even a new driver is installed, but the buildin driver do not support M1 processor as you known. we have no right to remove the buildin driver and no right to force the OS load new driver instead. an OS update would be needed to solve this issue.
we had reported this problem to Apple when we test OS11 beta versions before. it is a minor problem under x86 machines because the buildin driver works with x86 machines, but it become a big problem on M1 machines.
we are working on a temporary solution before OS update available now, i will let you know when it available. sorry for the inconvenience.