For databases, many like postgres have a ping / ready command you can use to ensure it’s up and not have the overhead of an actual query! Redis is the same way (I feel like pg and redis health checks covers a lot of the common stack patterns)

Encrypted Matrix or mattermost server with jitsi?

Depends how close they are. Most of my friends (that are into self-hosting and collecting Linux ISOs) are across the country / world. So mailing encrypted SSDs works best for large transfers and nextcloud for small transfers