Welcome to the community, @Kyle_Simmons!
The rich text field does not support HTML tags. It supports a small subset of markdown syntax while you are manually typing text within the cell, but even that small subset of markdown doesn’t work for copying & pasting markdown into cells or for importing markdown data into cells. (In fact, Airtable doesn’t allow importing into rich text fields at all.)
The only way to get markdown automatically recognized by the rich text field is to use Airtable’s REST API, which you can access via scripting, or by using a low-code automation tool like Zapier.com or Make.com.
You could even use Make’s HTML to Markdown converter to convert your HTML to markdown before sending it to Airtable, but again, Airtable doesn’t support all markdown functions so you’d probably need to test this out to see how good your final results are.
Make can be extremely difficult to figure out, but if you have a budget and can hire an expert consultant to help you, please feel free to reach out to me at scottworld.com to help you automate this process for you.
I haven’t tried this out with Zapier, but I’m assuming that similar tools exist there.
There are also scripting experts in these forums who could help you with this, if you choose to do it via scripting.