The problem is solved by now: As conclusion I'd like to say that the recommendation of Toshiba THNSNJ128G8NU for a DELL Optiplex 9020M is not realizable without risk and restrictions.   Anyhow.... the DELL community is great!  Thank you very, very, very much for your nice an professional hints! Greetz Peter    
Hi DELL Community, last days I upgraded my 9020m with a M.2 SATA Toshiba THNSNJ128G8NU SSD Drive. Following the instructions and pictures in this thread I successfully installed the SSD. [URL] The drive is looking exactly like on the pictures in the linked support thread. The BIOS is Version A19 (19 Jul 2019). I want to configure the new M.2 SSD as secondary drive besides the booting Micron SATA SSD. The Problem: I cannot find the M.2 SSD in BIOS setup. It is not detected, there is no possibility to configure the drive.  Ubuntu Linux (installed OS) doesn't detect the M.2 SSD, too. Does anyone have an advice how to use the drive?     
9020m -- Having trouble to find the M.2 SATA SSD in BIOS