I bought the game Flashback, because I wanted to play it on the original DOS hardware. I already own many games from GOG, which are actually running in the DOSBox and they mostly can be easily used on the real retro hardware. Unfortunately, I was disappointed by Flashback so far, because it seems only to have the Unity "remastered" version, which is useless for me. Is it possible to get the original DOS Version from GOG as well?

Nope. This is not simply a way of playing the old game in new systems (like all the DOS game releases from GOG that use DOSBox) but a remaster, as you say. See my post here for more info

Using the files from this release tough, you can play FB with REminiscence, following the instructions in this post... But that is still just playing in Windows.

If I was in your situation having bought the game I would feel no problem, morally speaking, to get a DOS version and play with it in any way I saw fit. Luckily I still have my original copy, although these days I'm not playing in vintage hardware, but using PCem, and Munt for MT-32 music.

Original Floppy DOS Version had its Copy Protection very (!) nastily implemented, which is possibly the reason why GOG gave up on it - it is very hard (as in time consuming) to fully deprotect it.

Maybe I can share more details in a few weeks as I look into it (German Release). Do not get your hopes up though.

Regards

I have something I could share with you regarding that. It is for the English release, and it makes it a breeze to get through it.