Hi Phil and welcome aboard.
Looking forward to seeing some shots from up north - I've missed getting up there this year (and for the past few years beforehand, for an entirely different set of reasons i'll not go into) - somehow the "being confined to barracks" has made me miss the wide open spaces more I think...
How's the D3400 working out...
It's a big transition from cameraphones and even bridge cameras to a full on DSLR - often people find that they almost end up taking a step backwards in terms of their results, purely because the camera has so many more options - and - often because they think "oh, i can take full control of the camera now, I'd better try and shoot everything in manual mode..." Personally, I don't subscribe to that - I'd "stick it on P mode" and get to grips with the rest of the options - auto or manual focus - and whatever lenses you have - when you're comfortable with that, start "adding in" extra bits - try Aperture Priority (A on the dial) for stuff like portraits where you want a shallow depth of field, set the Aperture and let the camera do the rest. Or - for stuff where you need to "stop movement" try Shutter Speed priority (S on the dial). Play around with those options, get to know the hardware. Add in using exposure compensation for (say) backlighting, or for confusing scenes with high contrasts (a classic being the typical wedding Bride and Groom Shot - he's in a dark suit, she's in a white dress... Whatever you do, expose to get the details in the dress - she's going to care about it, he's not going to give a stuff if the pictures show the dark red shadow-stripes in the dark blue suit...)
And when you've got the hang of those, you'll already be thinking "hang on, I need to pin down more than just one part of the "exposure triangle" - what's that you say ... have a play here -
https://dima.fi/exposure/ - and at that point, manual comes into its own...
modern cameras are marvelous bits of kit, speaking as someone who started shooting SLR Cameras back in the mid 70's with a completely manual film camera, they're just incredible. Don't be too precious about "must shoot manual" - an awful lot of pro's I know, won't use manual unless they're doing something fairly "outside the normal" , or are working in a studio with controlled studio flash lighting... Not dismissing it completely, just saying it's not something that you "must do" with a SLR - it's just another tool in the toolkit, and trying to keep to manual only will probably slow your learning curve of the new toy...