D&D 5E Brawny rogue

[UngeheuerLich]

We're allowed to disagree. I would be interested in seeing any rogue you have played or DMd that didn't have at least a 12 dex.

12 Dex is a low bar and recommended for every rogue. I would even recommend 13 Dex at least, so you can mutliclass out to and get some abilities that are useful for str based rogue.
Also 13 dex allows to take the moderately armored feat, which brings it to a perfect 14 for medium armor.

An 8 Dex rogue is not something to really consider, as it is so niche that it is rather a thought experiment, nit something anyone would really want to play.

The medium armor rogue could easily be achieved with variant human:

17 Str
14 Dex
14 Con
8 Int
10 Wis
12 Cha

Or something like this.

I personally would not take variant human and be content with light armor till level 4.

Maybe half orc or goliath

16 Str
13 Dex
16 Con
8 Int
10 Wis
12 Cha

Survivabilty in level 1 to 3 is more dependend on HP than AC in my experience.
Half Orc and Goliath both have great abilities to save against sudden unconsciousness.