So there’s a big bug with any Qt5 program, the internet, and WINE. See also: bugs.winehq.org/show_bug.cgi?id=49531
There’s a potential fix here: forum.winehq.org/viewtopic.php? … 7&p=132039
A quick and dirty fix is to download the 5.7 lutris runner and use that. (You don’t need to install it, just unzip it, and run scrivener with that version of WINE.)
I’m building WINE 6.3 with that patch to see if things are fixed. It seems like a fairly major one that’s affecting a lot of high-profile things like the EVE online patcher, so odds are good it’ll be addressed.
If you feel like helping them out, try the patch and post in bugzilla. The WINE folks are pretty nice, and will prompt you, if you don’t know what they’re asking for. 
But hopefully this gets fixed before 3.0 goes live, because it has the potentiality to affect the Paddle licensing server, too. Worst case, use the 5.7 lutris build, authenticate to get your copy registered, and then you should be good to go with the regular WINE on your system. (I’m spitballing, because I don’t think Scrivener has to be always online, and I don’t think the Paddle code is in Scrivener 3.0 yet.)
How to run Scrivener with a custom version of WINE that isn’t your system one: WINEPREFIX=/home/you/.path_to_your_prefix /home/you/wine_whatever_lutris_is_called/bin/wine /path/to/scriveners/binary/Scrivener/Scrivener.exe.
Like you shouldn’t need to use this for a daily thing, just to get updates and authenticate your copy, if this is still an issue by then.