Corner frames on the inside made of wood?

Hello everyone, we are currently renovating a house and have actually removed all the door frames (steel frames) except in the bathroom (since the bathrooms remain).

Unfortunately, we have passages where only a corner frame will fit, as the wall connection is on the end side. Since I only find steel corner frames online, I wanted to ask if you have any ideas on how this could be solved differently? Specifically, in the middle you see a former apartment door (there used to be two apartments in the house, but we now occupy both floors). You can see that the frame is way too large. So only a corner frame will fit there. Do you have any ideas how to solve this without a steel frame?

I will also go to a door dealer next week and ask there.

Best regards Matt

PS: I am just wondering why we didn’t knock down the passage or the wall? I don’t know right now.

I unfortunately can't contribute much to your question, but your slots for the cables are anything but good for the house. I myself don't always follow every standard and am more of a practitioner than a theorist, but that would give me a bad feeling. Not only that data/power lines are placed together... I probably wouldn't have made 2 slots either. But the fact that the slots run completely around horizontally throughout the entire room is a significant narrowing of the masonry cross-section. If you have other rooms, then think about an alternative before your upper floor soon becomes the ground floor.

Hi danifx, it just looks like that
The load-bearing walls are 24cm thick and plastered with 3cm.
We made grooves with 35mm. So no problem, according to our structural engineer as well
But thanks for pointing that out!
Regarding data cable and electricity together: We also considered that, but that would have been too much for us. So it has to work like this now, otherwise there will be WLAN.
Regards
Mattes

Maybe one of you has an idea regarding [Blockzarge] or [Eckzarge]?
Best regards
Mattes