I'm using it on Qubes, which I've never had the slightest problem with until Lithium Luna. I ended up reinstalling everything from scratch for a different reason (and by 'everything' I mean everything, OS included), and when I installed 0.12.0.0 and downloaded the entire blockchain, etc I see I'm unable to transfer any funds because the wallet's 'not connecting to the daemon'.
I used the CLI, and when that didn't work I tried the GUI. I run into the same problem with both. With the CLI, though, I can see what monerod is doing, and guess what? Its running just fine. "SYNCHRONIZED OK" and all that. I get a lot of "ALTERNATE BLOCK" notifications as well, but I know that's completely normal and nothing to be worried about.
Oh! And did I mention Lithium Luna has this same exact problem on my iMac? Yeah, it's getting kinda frustrating at this point because I promised my brother I'd send him some Monero after hounding him to get into it for months. Needless to say this hasn't been the greatest advert for the currency.
Here's some output:
2018-05-12 14:23:48.894 754a7d0a3700 ERROR net.http contrib/epee/include/net/http_client.h:456 Unexpected recv fail 2018-05-12 14:23:48.895 754a7d0a3700 ERROR wallet.wallet2 src/wallet/wallet2.cpp:5857 !r. THROW EXCEPTION: error::no_connection_to_daemon 2018-05-12 14:23:48.895 754a7d0a3700 WARN net.http src/wallet/wallet_errors.h:794 /home/vagrant/slave/monero-gui-ubuntu-amd64/build/monero/src/wallet/wallet2.cpp:5857:N5tools5error23no_connection_to_daemonE: no connection to daemon, request = transfer_selected