Gravel / Gravé / Gnarmac / Groad / ATB

Hi guys, not sure if this is the right thread for it but decided to post it here instead. Was hoping you can help me out with choosing a frame. More and more, I've been travelling outside London/UK with my road bike in tow but most of the paths I encounter are off road track so I think it's better if I just get one of these gravel frames. My road bike can only handle a max 28c tyre and its already tight at this point.

Steel or titanium would be preferred. Able to run 650b is a massive plus, would like to try disc brake. Thru axles would be nice. Fenders.
Here's a list of frames I've been looking at (budget is roughly 1500,can go higher for the right frame)

1. Mason bokeh - that price and aluminum kind of puts me off unless somebody can vouch for it.
   
2. Soma wolverine - sizing is really wierd on these frames. Top tube is really long even on the smallest size.
   
3. Kona Roadhouse - I was told it can only fit a 28c with mudguards. Shame as it looks really good.
   
4. Ritchey Swiss cross disc - looks really good this.
   
5. Niner rlt Steel - pf30 puts me off this frame.
   
6. Custom? Never really thought about going custom as I don't have the patience to wait for 3-5 months.
   
7. Any other frames in mind?
   
   

I apologize of this is the wrong place to ask, was debating whether is hold post this on recommend me a road bike.

Thanks!