When someone tries to schedule a meeting during my focus hours, I decline it.

When someone DMs me about an issue they should post in the support channel, I link them to the support channel. If they insist, I link them to it again, and I inform my team not to respond to DMs from that person.

Do not engage with people who think their time is more important than yours; if you do, insist on wasting their time in equal amounts.