Below are several SEO-related website accepting free guest posts with backlinks:
Answerout.com | Submission Guidelines | Ahrefs Rank: 351,878 | DR: 56
SEO-Hacker.com | Submit | Ahrefs Rank: 36,701 | DR: 75
Pole Position Marketing | Write for us | Ahrefs Rank: 57,905 | DR: 73
TechWyse | Write for us | Ahrefs Rank: 71,033 | DR: 72
MarketingTechNews | Write for us | Ahrefs Rank: 26,522 | DR: 76
Mangools Blog | Write for us | Ahrefs Rank: 29,766 | DR: 76
Linkody Blog | Write for us | Ahrefs Rank: 72,656 | DR: 72
RankWatch Blog | Write for us | Ahrefs Rank: 87,053 | DR: 71
Serpstat Blog | Submit | Ahrefs Rank: 18,456 | DR: 78
Jeffbullas’s Blog | Writing Process | Ahrefs Rank: 8,371 | DR: 82
Search Engine Watch | Become a Contributor | Ahrefs Rank: 2,267 | DR: 88
Search Engine Land | Contribute | Ahrefs Rank: 883 | DR: 91
Search Engine Roundtable | Contact us | Ahrefs Rank: 5,630 | DR: 84
SEOBlog.com | Contribute | Ahrefs Rank: 69,728 | DR: 72
Mainstreethost.com | Contribute | Ahrefs Rank: 102,410 | DR: 70
ResultFirst | Write for us | Ahrefs Rank: 998,976 | DR: 45
Seomator | Write for us | Ahrefs Rank: 131,447 | DR: 67
skyje | Write for Us | Ahrefs Rank: 439,279 | DR: 54
EZ Rankings | Write for us | Ahrefs Rank: 114,288 | DR: 69