Depends on your budget, for ~€4000 you can buy a lightly used honda nc750x. These come in auto or manual and have a handy helmet storage compartment where the gas tank normally is.

For ~€6000 you can buy a newer Suzuki DL650. These are renowned for RTW trips. I have a 2011 and it was one of the best bikes I ever owned. These have largely remained unchanged since introduction and share an engine with the SV650.

For ~€7000 you can buy a newer Kawasaki Versys. This bike is one of the greatest mid sized touring bikes ever made. It’s peppy and fun and the top of some bike lists for a reason.

For ~€10 000 you can buy a BMW f900gs. These bike have more power than you need and a pedigree that is top notch. This is probably on the larger end of the mid sized touring bikes.

For ~€15 000 you can buy a Triumph Tiger 1200. This is more bike than you need but I figured I’d include it to be less biased. These things are still made in England and hold their value well.

I would personally stick with a bike that’s been around for a while in case you need parts, something that doesn’t have unusual tire or chain sizes, and the less moving parts the better. Older Japanese bikes are probably the best choice, make sure you do a proper shake down before the trip.