Visual Studio 8+ for macOS requires Mono framework version 5.18.1.24+
Unity Hub Keeps installing a dated version of Mono Framework 5.16 which prevents VS from launching.
This causes Visual Studio to reference the incorrect Mono framework version until a relink from 5.16 to 5.18 is done which resolves the issue. This change doesn’t affect the running of Unity but it is a nuisance every time a new version of Unity is installed via the Hub which kills VS.
Second this. Super irritating, sticking with vs2017 for now.
Finally I understand who kills VS for Mac. 
Having this issue constantly. Is there a fix?
Thanks for pointing this out, the team has been notified. Could you please submit a bug report for this issue through the Hub bug reporter as well?
Oh great - I already got used to always reinstalling the mono framework after a new unity version and hoped that someone has already reported this annoying issue
So hopefully this is being looked at now, thanks!
Yeah, this is really annoying. Hope it gets fixed.
Cheers, Michael B
2019.1.10f sadly not yet fixed
I already submitted it (Case 1158032) almost 2 months ago (27/05)
The team is looking into it. You can track the status of the issue here:
@LeonhardP I assume this also affects Visual Studio Code on Mac complaining about not being able to load the cs project successfully when using the standard Omnisharp extension for c# development? VSCode complains about the framework sdk not being right. We are currently downloading and installing Mono (5.18.1 Visual Studio Channel version from the Mono site).
Did this resolve the issue?
For macOS VSCode + Omnisharp loading Unity .csproj files without complaining, yes, manually installing Mono seems to make it happy
In the issue tracker it’s marked as resolved with Hub 2.0.4, but I still get the error after installing 2019.1.14 in Hub 2.1.0. Added a comment to issue tracker.
Thanks, I reopened the ticket.