I've spent a lot of time thinking about this too. Generally for dedicated tourers people tend to prefer cr-mo steel frames, for durability, comfort and repairability, but it is by no means a hard and fast rule if you'd rather get a new/newer aluminium bike. Lot of people prefer 26" wheels for the ease of finding spare spokes, inner tubes, tyres and wheels but that's less of a factor in Europe really.
On a budget I'd say there's really two approaches you can take, bike wise. You can get an older road bike which was either intended for touring, or can be adapted for it with P clips and the like. Advantages of which being that they're generally quite fast/efficient on the road, and come with drop bars which are generally fairly comfortable/well suited for touring. Disadvantages; a lot of 70s/80s steel road bikes also come with steel wheels, which are a pile of rubbish and it's a bit of an investment on top to replace them immediately, and similar story with the shifters usually. Stem shifters are a pain, bar ends are the best but downtube shifters are okay, and could allow you to switch to bar ends of brifters if you so desire. This is probably the approach to take if you're the sort of person who would religiously plan every day and have specific distance targets and destinations to reach.
The alternative is to go down the road a lot of the higher end modern touring bikes seem to, which is to construct some sort of mountain bike/road bike Frankenstein's monster. See things like the Surly Troll, Genesis Vagabond, Trek 920 etc. which you can somewhat approximate on a budget by finding a solid cr-mo mountain bike frameset and building something up around it, with newer wheels, groupset, and either drop bars or butterfly/swept back bars if you prefer. This wouldn't be as fast on the road, but would likely be a lot more versatile and suited to someone who wants the option to explore some less than perfectly paved paths "just to see where they go". It would have a more upright riding position, which would put you in the wind more but can be a lot more comfortable on the neck/back when spending long hours in the saddle. And mountain bike groupsets are typically far better suited to carrying heavy loads up long, steep hills - hence why some people put them (or parts of them) on road bike tourers too. With older MTB frames, you're probably stuck with canti brakes or maybe mini-Vs, but they're not so bad when well adjusted and there are some good performing modern ones developed for cyclocross.
Lot of this depends how handy you are with a hex key, of course. Local bicycle cooperatives are worth looking into.
On phone charging, might be cheaper/simpler to have a fairly large solar panel you can strap to the top of your rack instead of messing with hubs, which can be expensive and pretty hit and miss. But you can generally get a few days charge out of a reasonably cheap external battery pack, if you think you might be staying somewhere you could charge it that often.
acific but this is the only one I can see now, it does discuss many of his gear choices though: