If you cannot ignore slack in the evening, weekends, you gotta be bad at your job. If you are good, employer won't want to replace you and you can condition them to respect boundaries.

"I sent you a message, why didn't you respond?"

"I didn't see it."

"What were you doing?"

"Cooking. Food shopping. You know, the essentials to survive"

Not that I'd elaborate. I much prefer the "I had plans/a prior engagement".

If they ask, "I cannot really discuss this, it's private"