Shopify does not provide any ready-made solution for applying automatic discounts based on customer tags. You can use Shopify Flow, but many stores find it difficult to use it as well, and Shopify allows only one automatic discount.
The easiest solution is to use the Vista Checkout Rules & Discounts app, which allows conditional automatic discounts. You can select the customer tag condition -> add your customer tags and save on the discount.
It takes a minute to set up the rules.
Here is a quick video to create an automatic discount using a customer tag.
Earlier, a lot of Shopify stores used to achieve this using Shopify scripts, but now Shopify has deprecated Shopify Scripts and has provided faster and reliable Shopify functions.
The Vista Checkout Rules app uses the Shopify function to provide a fast and reliable solution for running automatic discounts.