Ask the bods in Germany if their product is MIB friendly. Post the answer here for future reference.
As for why a bod from overseas is insured to drive a hire car in the UK, as per post #5. It’s because the hiring companies (Herz, for example) spends a lot of money each year with an insurer to ensure that insurance is in place. The premiums may run into the multiple millions, so much that Herz for example run the product through their own in-house insurance vehicle, called a ‘captive’.
https://www.captive.com/news/2018/08/08/what-is-captive-insurance Herz’s captive is called Probus, based in Dublin
https://www.hertz.com/rentacar/misc/simpleIndex.jsp?targetPage=probus_about.xml
When it comes to individual bods trying to do the same thing (again post #5) it’s much more difficult to do as there is all but zero demand for the product. Adrian Flux seems to have found an insurer capable of providing the cover, whilst the German insurance provider seems (if the internet responses are up-to-date and accurate) appears to have found a way of doing it too, presumably primarily aimed visitors to Germany wanting to do the same thing. For the purposes of this thread, let’s assume that the German insurance provider is as good at their job at arranging locally compliant (EU wide) insurance as Flux is. If they are not then eventually the German equivalent of the FCA will catch up with them or not.
Following the link to
http://www.lobagola.com/green-card-insurance/eu-border-insurance.html it seems that this is an insurance provider who specialises in the same service as Flux but aimed primarily at the Southern European market. They appear to have teemed up with a bunch of local insurers to provide the service, presumably mirroring Flux’s service for bods bound to the UK.
Tour Insure
https://www.tourinsure.de/en/international-motor-insurance-and-frontier-insurance/car/usa-en-2 seem to have teamed up with Axa, one of the true pan-European Motor insurers. A British friend used Axa to insure his Nepalese bought and registered (the number plate was a load of squiggles) when he rode it back into Europe from Nepal, from where he’d bought the thing initially. The key difference about the German provider seems to be that their product is aimed at bods insuring their own vehicle when abroad, not bods arriving in Europe to ride a borrowed bike.
TourInsure is the expert for international motor insurance and frontier insurance. Whether you are on the road in your own car, camper or on your own motorcycle, we have the ideal insurance for your vehicle.
Which is not what the OP is seeking to do.