How to start comfrey from seed

This is what I'll try.  From https://growingorganic.com/growing-guide/comfrey/.

"Place seeds in moist sand, vermiculite, coconut coir, potting soil, soilless potting mix, or paper towel. After this, place it in a baggie, cloth bag, or glass jar with lid. You will want to avoid placing in a paper towel if you can, as it is sterile and does not contain endogenous growth hormones that encourage germination. Additionally, don’t just use peat moss alone as it is too acidic.

To assist your seeds in germinating, add a little kelp (seaweed) to the medium. Since kelp has naturally occurring growth hormones it will help seeds germinate. Additionally, it can help prevent damping off.

Now, simply place the bag or jar in your refrigerator. You will want to keep them in there for the next 30 days (up to 60 days maximum). The reason you are doing this is to break the dormancy of the seeds by creating winter-like conditions. Do not put them in your freezer when moist though.

After this, you will want to plant outside once the soil temperature is between 68-80 degrees Fahrenheit. Just remember, germination results are better when first planted in a warm greenhouse or sunny window.

While the seed is still thinking about sprouting try to keep soil temperature between 68-80 degrees Fahrenheit. If needed, you can use supplemental heat such as a heat lamp or horticulture heat pads. You will want to adjust the thermostat for 70 to 80 degrees.

Since we’ve now created the perfect environment for the seeds to sprout, you should seed them germinate in 10-15 days."

Also http://www.nantahala-farm.com/comfrey-growing2-s.shtml.