Can a universal derailleur hanger be a suitable long term solution? I've recently snapped my derailleur hanger for an old Apollo Raceline Peleton road bike. Have had no luck sourcing a replacement that fits, and neither have local bike shop. 

Has anyone been in a similar situation and used a universal derailleur hanger to suffice? 

Could something like this work? https://problemsolversbike.com/products/drivetrain/universal_-_21655
The particular derailleur hanger you linked is not going to fit your bike, I'm afraid. It's more of use with the bicycles that have the almost horizontal forward-facing dropouts.

What you can do is take the remainings of the hanger you have, inspect it for any markings and on a page like https://www.internet-bikes.com/versnellingen/derailleurhangers (I'm not affiliated with them, though I buy my parts there) find the closest match to your broken part. 

Or even take your search a step further and browse the webpage of the manufacturer of those hangers and match your part with their catalogue: http://www.marwi-eu.com/gh-catalogue.php (again, not affiliated).

Good luck!