Wrong.
If he'd bother to RTFL he might even figure out how wrong he is.
The short answer is no.
Here's a PDF of Act 35.
Here's a link to search WI statutes.
Here are the parts you particularly want to read, understand, & probably even print out to send to the management company when you write to complain about the property manager.
(Or if he is the owner, give him a copy + that link to the search page for the statutes.)
Always best to go to the source documents.
That opinion blog from (apparently) a lawyer is OK, but he's not your lawyer & he's not giving you legal advice. If you want legal advice, check with the bar ass'n to see who in your area deals in landlord-tenant law, & if they have a free consult session or maybe how expensive 30min would be... and if the landlord insists on breaking the law, that lawyer will have a heads-up to be able to start filing a suit.
So the owner of the property is immune from legal liability if he doesn't interfere w/ you exercising your rights.
To everyone except lawyers, this also means that if a place prohibits you from protecting yourself & you're harmed, they're liable.
So even if he posts the building, or your apartment door, it doesn't affect you at all.
Carry openly or concealed. He can't do a thing about it, other than not renew your lease, & then you'd have quite the legal case against him (or the management company), esp. since peacefully exercising a protected civil right probably is not in the contract as a reason they can kick you out.
If people come to visit, you'd have to meet them at the door (
or their car, if they don't have a carry license), take their pistols, carry them to your apartment, & give them back. Reverse when they leave.
So visitors with carry licenses are immune from any signs telling them they can't carry on the apartment grounds.
You're immune because you live there, whether or not you have a license.
Again, a sign wouldn't apply to you, but would apply to your guests.
The sign has to be posted at every entrance.
The sign has to be at least 5x7". Not very big, & there's no standardization of design, which sucks. That's one thing that needs to be corrected in the next legislative session.