Can my belt drive frame be converted to a derailleur setup? I want to know whether my frame is compatible with any kind of derailleur hanger, as I want to install standard gears. Due to my Nexus 8 speed hub being really quite uncomfortable and faulty since getting the bike (it gradually got worse).
I can just invest into a Rohloff hub and all will be well, but that's a big chunk of money for me. I'd prefer to switch (if I can) to a simple derailleur system, which I can easily maintain too.
See this link for my exact bike, it's possible to zoom in on the rear dropout too, as below:
I know there's no direct fixture for a hanger, but are there alternative ways to fit hangers onto frames like this?
There is no good way. One could imagine ways of contriving a low-end claw-type derailleur on. Don't do that.
Nexus hubs are usually reliable. In some places in the world, there are lot running around without issue. That you've had chronic issues suggests either damage, defect, or a setup issue.
Some number of Nexus and Alfine bikes have made it into the world with mismatched cassette joints and shifters from the factory. It is a maddening problem until you've figured it out.
There are steps between what you have now and Rohloff, if it came to replacing the hub. I recommend taking it to a shop that really knows internal hubs. They are robust but have their quirks and unique procedures and things to check.