thelostkiwi

I have a copy of Tamron’s 150 - 600mm G2 lens. It has really good image quality and is easy to use. I have heard the one you are asking about is similar. Will you be able to test it?
The only drawback for me with my lens is after carrying it around for a while, it gets heavy and so on the tripod it goes. Also, it was not a FX mount lens, so I use a Fringer smart adapter, but that has never been a problem.

My first Fuji was the X-E3, it was bad to hold and I was often accidentally actuating buttons and controls.
I purchased the Fuji metal handgrip for it and found it was significantly improved. Then I disabled the Q button as I was often accidentally pressing it, I also disabled the touch screen.
I still own and use the camera 8 years later and it's been a great photographic tool.
Maybe look into a handgrip and some adjustments to the controls before you jump ship.

English Lavender 
 
Fuji X-T4 with Samyang 12mm AF

Spring time in the Charente Maritime.
X-T4 with 18-135. 

English Lavender 
 
Fuji X-T4 with Samyang 12mm AF

Sorry for late repy, i have only just seen this. I got myself a K&F one thanks again.

Plenty on eBay and Amazon.
 
The one I use is a KEF Concepts which works fine. 
Remember you will have no AF, no feedback of aperture and will need to stop the lens down manually. 
That all said vintage lenses are a bargain and you can get a very good lens for not much money. 
 
For example I paid £15 for a Carl Zeiss Jena 135mm f/3.5 lens in m42 fitment and it is pin sharp even wide open. Likewise Minolta MD 75-200 f/4.5 (£25), Minolta MD III 35-70 f/3.5 Macro (£20) and Rollei (Zeiss) 50mm f/1.8 HFT (essentially a Rollei QBM version of the C/Y 50mm 1.7).
Minolta in the 1970s worked with Leica and both the MD lenses above are identical optically to their Leica SLR counterparts at a fraction of the price. Likewise Zeiss worked with both Rollei and Contax (though Rolleinar and Yashica lenses are not the same as the Zeiss ones). 
 

Bizarre to make your camera purchase decision on an app that'll probably be rarely used. 
 
I've used the remote app maybe 3 times in 2 years. Would I base my purchasing decisions on that experience? No. 

Spring time in the Charente Maritime.
X-T4 with 18-135. 

English Lavender 
 
Fuji X-T4 with Samyang 12mm AF

Cooks Ridge Gwynne Creek Loop hike Cape Perpetua, Oregon. X-T50, Fuji 16mm F2.8, RealaAce.

Buachaille Etive Mor, Glencoe, Scotland
Fuji X-Pro 2 & Fuji 16mm f1.4
 
20160530 - Glencoe (Buachaille Etive Mor) by Chris Mitchell, on Flickr

Saalach - Kurz vor dem Sturm by papedo_pp, auf Flickr

Sunrise in the Netherlands. Fuji XT-1, Samyang 12mm/f2, Lee Seven5 Soft ND Grad 6.
 
 

Fuji X-E1 + 10-24/4 

Light&Stripes II
 

Mystic Morning III
Wolfgangsee Austria / 10-24mm
 

Light&Stripes
 

Starry Eruption - The Milky Way on Top of Mountain Fuji
 
Starry Eruption by Mahalarp Teeradechyothin, on Flickr

in the middle of the way by JS-photographie, auf Flickr
 
X-E1 with XF 14

Another one. Near Probolingo, Indonesia. XT-1 with 18-135.

Fuji XE 2 35/F1.4
 
Marina Bay by Night by gerlesion, on Flickr

Fujinon 56mm does landscape (X-T1):
 

Foggy dawn 1 by Pascal van Gerven, on Flickr
 

Foggy dawn 2 by Pascal van Gerven, on Flickr