If you have read some articles from me, it will be clear by now i have become a Fujifilm X camera and Olympus OM Zuiko lens fan, however, most of my photographic life I have worked with Pentax and Pentax lenses, and even today my 6 to 7y. old Pentax K3 Dslr is still one of my main cameras. An Optical Viewfinder and In Camera Image Stabilization are still major assets compared to the advantages of many mirrorless cameras.
A camera comparison of the 5y younger Fuji X-T30 at https://cameradecision.com/compare/Fujifilm-X-T30-vs-Pentax-K-3 makes that painfully clear.
That said, shooting manually with a Fujifilm X camera also has its advantages.
The weight difference of almost half a kilo, compactness,
focus peaking with image magnification and the typical Fujifilm “out of camera” image quality, just to name a few.
Pentax K3, Pentax K5
Sigma 150/500mm, Pentax 50/300mm WR, Pentax 18/135mm WR, Sigma 17/50mm f2.8, Samyang 35mm f1.4
Fujifilm X :
Fujifilm X-100, Fujifilm X-E1, Fujifilm X-T10, Fujifilm X-T20, Fujifilm X-T1, Fujifilm X-A3
Fujinon XF 27mm f2.8 – Fujinon XF 18-135mm
Olympus OM :
Olympus OM D E M10 Mark I
Olympus OM1 – OM2 – OM10 – OM20 – OM40, Olympus Pen FT, Olympus OM2000 2x
Olympus OM Zuiko prime lenses : 21mm f3.5, 24mm f2.8, 28mm f2.8, 28mm f3.5, 35mm f2.8, 50mm f1.8, 50mm f3.5 macro, 100mm f2.8, 135mm f3.5, 200mm f4, 300mm f4.5
Olympus OM Zuiko zoom lenses : 35/70mm f3.5-4.5, 35/70mm f4, 70/150mm f4, 85/250mm f5
Other Lenses X Mount :
7Artisans 7,5mm f/2.8 Fuji X
Samyang 12mm f/2.0 NCS CS Fuji X
7Artisans 25mm f1.8
Other Gear :
Nikon F60 28-100mm
And a whole lot of different brands of classic prime lenses.