I have a custom DOI URI defined in Preferences > Web search on version 5.11. It works appropriately, going through my specified link instead of through https://doi.org/ . However, when I export an html list or table of entries, the custom URI is disregarded, and the DOI is appended to https://doi.org/ and encoded as the “DOI” link.
HI, thanks for bringing this to our attention.
There is actually a TODO in that part of the code where exactly it says the DOI formatter should respect the custom base URL 
I will try to look into it in the next days. At least for the export, there could be an option to pass the value from the preferences.
@iversoneb Hi, the issue is now resolved in the latest development version:
https://builds.jabref.org/main/
Remember to make a backup of your library before trying out the new version