This.

Especially in the souther parts of Germany, many mountain roads in Austria, Switzerland and parts of the french Alps and Vogeses have massisve protests from locals, due to bikes beeing too loud. The problem became even bigger throughout C19, as biking was one of the few activities, people were able to do. Bike traffic and noise pollution skyrocketted. Now there are lots of places where bikes are temporarily not allowed to drive (mostly weekends), entire regions where noise limits are implemented and where bikes are constantly controlled for noise violations. Cops test your bike with a calibrated microphone to check, whether the sound aligns to what is written in the bike´s documents. Not passing that test will at best end up in a hefty fine. If violation is too high, your bike can be declared not road worthy/illigal in that area and may be trailered out of that zone (seen a news report on that topic, where a local needed to tow his totally legal bike from his house out of the no bike/noise limit zone, to be allowed to use is.)

Check the legal noise emmissions requirements in Germany, Switzerland or Austria (I believe, these are the most restrictive) for your bike and try to match that with an OEM exhaust. Fines are very high for violations.

Not sure, how about this noise pollution reduction movement is proceeding in skandinavia, but if they are going the same route, their fining system can be much more expensive, as they calculate your fine by your income.

Enjoy your trip.

Edit:

https://www.dr-big-shop.de/46_Auspuff.html

This german shop offers so called "decibel eater" for your DR 650.

With a silent bike, a foreign plate and a polite attitude you´ll be most likely waved through all over Europe.

Edit2:
find a list of roads closed or with limited access a for bikes in Germany and Austria here:

https://www.motorradundreisen.de/motorradfahrverbot/