best mirrorless landscape/portrait lens.

[Dmcd3055]

what is the best mirrorless landscape/portrait lens. I have an R5 TIA

[shadowsports]

Greetings,

You're asking to cover a fairly broad spectrum.  What's is your budget?

I love my 15-35 f2.8 for landscapes, architecture and street photography.

For portraiture, I'd probably want something in a 85-135 mm FL.

Single lens solution.  A compromise could be a 24-105 f4, or 24-240.

These may not offer as much bokeh for portraits, but in a pinch would work. If you want maximum results this is more likely a 2 lens endeavor.   

[Tronhard]

First, we come to the question do you want to have zoom lenses or primes? 
Conventional wisdom would suggest that primes will have a smaller f/stop value - thus allow a shallower DoF and work in lower light, and may be sharper.  Others argue that the difference is now much narrower than traditionally, and there is a benefit to having the ability to zoom for composition.
Thus, you are looking at two lens types. My point is that there is no definitive answer, but if you would like to narrow the field a bit by indicating if you prefer zooms or primes that might help us.

With landscape and portraiture you are looking at two very divergent contexts.  Given you have an R5, I assume you are prepared to budget a bit in your optics, considering they represent the more critical investment.

Most people shooting landscapes will go for a fairly wide angle lens and a medium to high f/stop value to get it all in focus.   My personal favourite is the RF 14-35L f/4 IS lens.  Beautiful lens, weather sealed, small, light, stabilized, constant aperture, and takes a standard 77mm filter - which is great for CPL and ND filters .  The zoom range gives one a lot to play with.  Note that like many new lenses, this uses a combination of optical and computational photography to achieve outstanding results in a compact, light and affordable format.  This is essentially a situation where dedicated cameras are finally catching up with cell phones in that respect.  The image correction is done in-camera for composing and for JPG files, while it will be done to RAW files as they import to PP software like Photoshop and Lightroom.  The image look absolutely fine after lens corrections.

For portraiture, a moderate telephoto >= 85mm, up to say 200mm, with a very wide aperture, thus small f/stop value would be favoured.  A favourite for prime users is the RF 100mm f/2.8 L MACRO IS USM, or in zooms the RF24-105 L IS USM f/4 or f/2.8 variants.  If you want longer reach then the RF 70-200 f/2.8L IS USM would also be an interesting unit to consider.

I agree with Rick that if you want just one lens to cover the lot, the RF 24-240 IS USM super zoom is an amazing piece of kit.  I have it and love it for its flexibility and good results.  Absolutely, it does have the wide aperture of the more restricted L zooms or primes, but as you zoom out your DoF narrows, so it rather counterbalances the increasing f/stop value.  This lens too uses computational photography to get great results at a reasonable price and light weight.  One benefit of this method is that such lenses can be updated using firmware, which is rather brilliant.