Hello.
I have recently tested an interesting adapter: K&F Concept PK/DA-NIK Z.
It's a 'dump' adapter without any electronic. It's made of metal and it looks sturdy.
It has a ring to control aperture. So it's adequate if you have a lens without aperture ring and want to use it with your Z camera.
The aperture ring have 7 positions, so you just can have an idea of what is the lens aperture.
Here you have the adapter attached to my DA *50-135 (the last piece of Pentax equipment I still own).
The adapter is quite stiff and the first times it's difficult to turn it on the Pentax side,
I tested it on my Z6 II.
On camera, the best settings to use are: manual focusing and M mode. In M mode you use the front dial to control speed, also you can select AUTO ISO and exposure compensation.
One of the advantages or mirrorless can be seen here, when you select AUTO ISO: the camera exposes correctly without any info about the lens. You can dial exposure compensation if you want, and also you can turn the aperture ring and the camera will calculate a correct exposure for you, in real time.
Focusing is quite easy if you turn on the focus peak feature. Also you can use some button to see image at 100% to nail focus if you want. But in general focusing correctly and exposing correctly is an easy task.
PSA modes work, but you can only use the front dial to control exposure compensation and also select ISO AUTO on/off. Not very useful.
About handling this DSLR lens, is not very comformable with a Z6II if you want to use it hand held, but if you just want to use with a tripod, to take some landscape pics, then you can use it and it's a great experience.
This is not a FF lens, and it doesn't fill the sensor if you select FX mode, but it works great if DX mode. You can get about 10-12Mpix, that it's not a huge resolution, but can be enough for high quality video.
I'm not sure if I'll keep the adapter, because I'm selling the lens. I just wanted to know if I could use my DA with my Z camera. Anyway it's not a expensive toy.
It's late and I haven't any interesting subject to photog, but I can confirm that you can take pictures with the adapter, no issues, as sharp as this lens can deliver.
Regards.