I suppose the info I need is, what is the maximum load a hybrid can take.
How long is a piece of string?
It depends on the frame itself. And the wheels. And the spokes - quality, weave and tension. And the tyres - size and pressure. And the road surfaces. And the speed. And the temperature. And the location of the weight. And the maintenance. And....
And then, even if the bike can "take" the load how comfortable will it be to ride or descend hairpins in the Alps or Pyrenees? How will it handle off-road?
https://www.gumtree.com/p/bicycles/trek-/1307311891
That's enough bike for what you want to do (so long as it fits).
At the very least it's enough bike to get you out, dipping your toes in overnight trips to help you figure out what you'll want to be bringing with you.
40 quid!
Use it, learn on it and if you want to get a "touring" bike, then you can sell it for probably the same as you paid for it.
Incidentally, if you look around on that site, you'll see a low mileage Ridgeback with 2 sets of Ortliebs for 550 quid!!
I've said it before; Getting out on a bike and going for a bit of a "tour" will teach you far more about what you need, don't need, what you like, don't like and what's really important.
Bike touring despite the name, is really not about the bike! It's about touring.
Indulge me....
The bike is only the base of the Bike Touring Pizza.
You have a choice of crispy or doughy, whatever your preference is. If you're not a weight weenie, go for a cheese injected crust

But the toppings that go on top - they're what make the Pizza! Oftentimes, if the toppings are good, it doesn't matter what type of base is underneath.
It seems you're trying to make the perfect pizza without trying any of the toppings to know what you like or don't like or what go together and what don't.
Instead, you're asking strangers on the internet what they like.
I'd never order a pizza that way!
I've toured from Holland to Spain, over the Pyrenees, followed the Camino de Santiago to Santiago (off-road), wandered the western coast of Spain and then back along the Northern coast of Spain (lots of mountains!) and back to NL on a no-name hybrid bike that cost me nothing other than a service.
In total that bike toured in 7 different countries and did about 12-15000 km fully loaded before a chainstay cracked (suspiciously where a stand had been attached).
That worked for me. I don't know if it will work for you.
It was stuck in mud about a foot deep along the Somme, rode through a flooded forest path that reached the top of my ortliebs near Pamplona, cruised down mountains at up to 70kmh in the Pyrenees (going up was not as fast!) and was pushed, dragged and sometimes carried over off-road hilltops.
All I needed from that bike was to be able to trust it to do what I wanted it to do. And it did.
It was of no use at the campsite in Sen Sebastian (on top of a hill) in the middle of the most wonderful thunderstorm! My tent was.
It was of no use when the campsite I headed to in France was closed - a friendly local was.
It was of no use in picking out a good place to eat - my nose was.
Now I tour on a rigid steel frame, 26 inch wheels for strength and dynohub efficiency. I've gone from 1,5 to 1,75 to 2,0 tyres, purely for comfort.
That's only somewhat useful to you until I add
I carry 4 panniers and a rack bag, total weight of about 25 kg.
That's only somewhat useful to you until I add
I also tour in winter and carry a largeish tent and full cooking gear for cooking real food, not re-hydrated stuff.
Other useful information to assess how useful my story is
My average daily distance and speed, (Average is 80-85 km per day, 18 kph)
My fitness level, (reasonable, I have a 42 km daily commute 5 days per week)
How long I cycle for per day, (I stop a lot, but probably an average of 5 hours per day)
No disrespect to anyone offering any advice on any of your threads but the advice they offer is from their perspective, including my own
If someone tells you that they toured on thin racing tyres, then it might be useful to know they were staying in hotels, carried less than 5 kg of gear and never rode in the rain!
If someone tells you that they had to have tubeless fat tyres, front suspension and a bear bell it would be good to know that they rode the Great Divide Mountain Bike trail.
If you want to keep your dream alive, you need to find your own perspective, otherwise 2 years out from your tour, your dream is going to drown in too much information.
Good Luck!