Catalina can see SATA drives but asks to erase them

[klaphd]

Dear community
I have done a fresh install of Catalina on an NVME ssd.
I use a normal SATA HD for EFI (as my motherboard does not recognize nvme ssd as boot device).
The problem I am having is that I can't see the partitions of my old HD (used for TimeMachine) and SSD (on which I installed Sierra) and if I plug them system tells me it's not readable and asks to erase (it happened already during installation).
Any hint on this problem?
Most of the rest seems to work, only thing is this issue, that blocks me from restoring my time-machine backup.

Many thanks

 

[klaphd]

The strange thing is that sometimes the SSD(or HD) gets recognized and I can see what's inside.
I was able to restore Time-Machine but I think some app or kexts messed up the system
So I've done a fresh install...and again, during installation the SSD was recognized, after the installation the drive is seen in Disk utility but it doesn't show its partition