In 2019 I sold one of my two blogs through Flippa. I'm really confused on if it's considered miscellaneous income or capital gains.

If you created the blog, it would be ordinary/miscellaneous income, subject to Social Security (Self-Employment) taxes - reported on Schedule C as Self-Employment. Any 2019 costs paid for creating (eg, paying someone to do graphics, or software purchased only for that blog) can be deducted from gross income as 'ordinary and necessary' expenses. 

@Rainman12 What if I purchase a blog (domain+content), that is making monthly revenue, would that be considered an intangible property and would need to amortize over 15 years? This website blog is not part of a bigger business, it is a standalone money making site.

The sale of intellectual property is now consider ordinary income.  It is no longer treated as a capital asset.