Squirrel proof feeders are also magpie and pigeon proof.
Don't mind magpies myself, highly intelligent birds they are. Amazing watching them use tools.
I'd suggest domestic cats and dogs cause much more harm to birds than magpies.
I've seen far too many long Tailed tits, sparrows, collard doves, wood pigeons, starlings, song thrushes - nests get had off, by them, to let the loss of any more smaller/song birds nests, go unchallenged. And as you say, they're clever, they don't come near the house, hence I think the other birds getting on to nesting closer to the house.
If you watch, magpies do the thinking and the working out and generally there is always a crow or two in the vicinity to gegg in and take the pickings.