Are Non-ED Visas for Thai Language Courses Currently Being Issued?

Most schools are closed and the ones that are open are teaching online. You would need to contact a school in your area to see if they are accepting students, AND if they can get the 90 day Non-ED visa inside the country.

Again that is between you, the school, the Ministry of Education AND the Immigration office in your area,

I know for a fact the MOE will still issue paperwork for you to LEAVE thailand and get an ED visa based on enrolling in a school BUT due to the entry restrictions you aren't gonna get back in right away..

Good Luck, you need to be talking to the schools you're considering studying at.

Make a post on a f/b page related to where you live here in thailand and you'll get answers. Believe me you're far from the first person to look at an ED visa as a way to further a stay here in thailand.