Hi @george life ! Welcome to the community :) you could achieve this with a 3rd party option, but not currently with Trello. When adding someone as a member of a board, you're giving them access to all cards on the board; there's no way to limit what cards they can see.
In terms of 3rd party options, you could look into the External Share power up which would be useful for external users that need view-only access. Another option is to create a secondary board, then automatically sync cards that have a specific label using Unito.
Hi @george life 👋
Welcome to the Community! Unfortunately, this is currently not a functionality on Trello. However, it could be a good feature request for the future... if this is something you would like to look into, I'd recommend reading Trello's guide on how to submit a feature request here >> https://help.trello.com/article/724-submitting-feature-requests-for-trello
I hope this helps but if you have any other questions just ask away 😃
All the best,