If I understand correctly, you want a bike that is similar in as many respects as possible to your Super Galaxy, but with clearance for wider tyres for the sort of gentle off-road touring you describe.
I think many suggestions will fall into one of two categories: expedition type touring bikes like the Surly Disc Trucker and Spa Wayfarer, and gravel bikes.
The Surly Disc Trucker and Spa Wayfarer will take up to 47mm tyres with mudguards (
https://www.spacycles.co.uk/m1b0s225p47 ... pd-Sora-STI and
https://www.spacycles.co.uk/m1b0s225p38 ... Cable-Disc). They are fairly heavily built, substantial frames and forks, and I think the Disc Trucker in particular is generally reckoned to handle better laden than unladen. I think you might find Disc Trucker and probably also the Wayfarer not as nice to ride unladen on tarmac as your Super Galaxy. I say that because I have a Wayfarer and a 1980s classic 531 Raleigh tourer, and the latter is a more flexible frame and smoother ride on tarmac, as well as being quite a bit lighter (>1 kg) because the disc brakes, burlier frame and rims and bigger tyres etc. all add up. However, like your Super Galaxy my Raleigh only has clearance for 32mm tyres, and the Wayfarer beats it hands down riding on gravel tracks.
There are so many differences now between various gravel bikes, that the term can be used for bikes that are very different. Some are more race oriented in terms of the frame, the geometry/handling, the (high) gearing and lightweight wheels, and some are more like light tourers (very lightweight if carbon/carbon forked) with large tyre clearances, e.g. I think 40mm clearance is the usual minimum now and many take 45mm. The Spa Elan in titanium (e.g.
https://www.spacycles.co.uk/m1b0s223p47 ... -Hydraulic) or steel takes up to 40mm tyres with mudguards, and is often recommended on here. If you visted Spa in Harrogate you could probably test ride a Wayfarer and Elan back to back, which would give you a good idea of the differences not just between those two bikes but also between those two classes of bikes. NB The Elan is one of the few gravel bikes with a tall head tube allowing fairly high bar placement with a carbon fork (carbon forks generally are limited to no more than 30mm of spacers below the stem).
I suspect however, that for the riding you want to do, it would make more sense to get a bike that could take wider tyres than the Elan and most other gravel bikes. From your description, the tyre clearance is the limiting factor on your Super Galaxy. I think that there is a danger that if you get a bike with 40mm or even 45mm tyre clearance, you will end up deciding that you would like the option of even wider. If at all possible I suggest you try some bikes with different width tyres on the sort of tracks you plan on riding.
There are a few niche bikes which give the option of wider tyres than Surly Disc Trucker and Spa Wayfarer, which are not burly expedition bikes (although will still be heavier than your SG), and which can be built with either drops or flat bars, subject to paying careful attention to the reach/top tube measurement and the frame size. For example,
Singular Peregrine -
https://singularcycles.com/products/peregrine (see also the Singular Gryphon)
Salsa Fargo -
https://www.salsacycles.com/bikes/road/Fargo
Genesis Vagabond -
https://www.genesisbikes.co.uk/genesis- ... vargn22500
Ritchey Ascent -
https://ritcheylogic.com/bike/frames/ascent-frameset - video review below.
The above bikes are not all alike, and they have various differences, e.g. Fargo has a carbon fork, Peregrine has an eccentric bottom bracket, Vagabond requires fiddling to fit a rear mudgaurd (there's a thread telling you how which you can find using the search function) and I think the Ascent might be similar.
