Ich have breach protocol 16 but i can put points into all skills.
No skill is greyed out.
But the texts says with breach protocol 20 i will unlock the level 20 skill.
Quickhacking works. The last skill is greyed out.

What perks you can buy depends on main attribute that a skill is tied to, not the skill's level itself.

Looks like a bug then. Should be greyed out.

It's not a bug. The breach perk is unlocked at level 16 of the "breach protocol" not the attribute and the quickhacking one is unlocked at level 20. Works as intended I would say.

Really? I thought all of those last perks only unlock at level 20 skill?

Not all of them.

But what is breach level 20 doing then?
It says it will unlock the last perk.

Ah now I get it. I was wrong, this does look like a bug where the unlock-level of the transmigration perk is set too low.