I was repeatedly getting the same error. But strangly when I started the owncloud client using ./owncloud --logfile ~/owncloud.txt command in the /Applications/owncloud.app/Contents/MacOS folder, I did not get the “Could not detect compatible server” error!
I post this here in case someone else runs into the same issue. Because the only other suggested solution was to add /owncloud to the end of the server url but that did not work for me.
By the way I updated my MacOS and owncloud client since I posted the trouble report. Versions are MacOS 15.3, and owncloud 5.3.2 as I got it to work!
UPDATE:
The solution has nothing to to do with the --logfile option but it does with starting the client from the command line. If I start the client with a double-click from Applications folder, my server connections to two servers (one pretty old version, one current) appear disconnected and can not connect; but if I start the client from the command line; it works fine.
This frustrated me for weeks now. Hopefully this helps someone else.