Is MiracleGro potting mix OK for my Dryopteris Marginalis (Marginal wood fern)
I would also like some additional comments about soil pH for this fern. How do I adjust the pH? Ferns sure do look unique!
Since you asked about potting soil, I'm assuming you're planning to put this fern into a pot; whether you want to keep it outside or inside I don't know. However, this article has general information which you can apply to either location: https://www.gardeningknowhow.com/houseplants/ferns-houseplants/growing-ferns-indoors.htm
You don't need to be too concerned with pH -- ordinary potting soil will be fine. However, many kinds of MG soils contain "moisture retentive" additives, which won't be good. You need a soil mixture that drains well. Try an African violet mix and add 1/2 again the volume in perlite.
Please be aware the marginal ferns are usually planted in the garden. Putting them in pots may not be successful, especially not in the house, although that's no reason not to try. Growing plants is a never-ending learning experience.