It seems like my derailleur hanger is bent. After a bit of research, it seems the Dolphin uses a Shimano Tourney Long Cage Rear Derailleur 6/7-speed or the model name is RD-TY300-SGS. I was wondering if anybody knew which derailleur hanger is compatible with it? Thanks!
Other than contacting Qualisports, you can take your bike to a shop and they can match it up visually. You can try visually matching it also; visit Wheels Manufacturing.
Temporarily (and even kinda permanently), if it is not bent too much, you can bend it back. It is best to use a derailleur hanger gauge tool to do it, but if you are careful and have a good eye, you can stick a hex key into the derailleur mounting bolt and use the hex key as a lever to bend it into alignment.
@iOsiris mine also arrived moderately bent due to damage/box intrusion during transit. I had emailed Qualisports with a short list of issues, but never received a response sadly on the make/model of hanger part of my list - I think it got lost in the shuffle. The hanger is very soft alloy. A bike shop should have a derailleur alignment tool, or might know what kind. Or if you want to carefully DIY...if you warm it up and wrap in masking tape and put it in a vice, or use pliers you might have success realigning it. I used very light torque pressure of the derailleur itself to guestimate realignment on mine so that it is functional for me. If you find out what type it is, I'd like to order a spare for my parts bucket. There are lots on Amazon that "look like it", but I don't know enough about these things. @Timpo is correct that Kyle Chittock at @BoltonEbikes might know the correct brand/type. Next time I have the rear wheel off, I'll take a better look and get the ruler out, but eyeballing it, it looks like 25mm between two upper screws - it seems similar in shape to the Trek/Giant hangers.