System won't boot with two screens connected

I was on Mint for a year now, and wanted to move to endeavour which i like pretty much.
However, after installing the OS from a USB stick, it won’t boot at all. When i disconnect one of my two screens, restart my computer and connect it again when it’s booted, it works fine. But this can’t be a permanent solution.
Waiting a few minutes does not work, trying to enter the terminal with ctrl+alt+f2 does not work.
I tried to update the nvidia drivers which didn’t helped either.
I did not find a similar problem, so i hope this question here is ok.
CPU: AMD Ryzen 5 2600X
GPU: Nvidia GTX1070

I recently upgraded from a similar setup - Ryzen 7 2700X, GTX1070 - so I know it works. This is very strange; someone should be around shortly to provide more help.