Here are a few to consider:
(Many online sites that offer free BOMs every year are still finishing up 2020 projects, and haven't announced anything for 2021 yet. But, it you watch their sites, or sign up for their newsletters, you can learn about them as soon as they begin.)
These have already posted new BOMs for 2021:
https://kimlapacek.com/2020/12/an-ol...onth-2021.html
Jen is doing another monthly color challenge:
https://patternsbyjen.blogspot.com/2...challenge.html
and
https://blog.fatquartershop.com/category/serendipity/
These haven't posted 2021 info yet, but have a free BOM every year:
suzysitcom always has at least one. right now, she is finishing up two BOMs, so she has not yet announced anything for 2021. I will be watching for it.
https://suzyssitcom.com/
pat sloan always has several. I keep an eye on her here:
https://www.ilovetomakequilts.com/
Wooly Block Adventure also happens every year. They haven't announced 2021 just yet.
https://quilterstrek.com/?page_id=19594
Claudia has a paper piece BOM each year. She is just finishing up the 2020 Snowflakes BOM, so have to watch for what she will do next
https://www.claudias-quilts.com/bom/bom.html
https://weallsew.com/?s=Block+of+the+Month
https://www.tuning-my-heart.com/we-c...-a-snowman-bom
Canadian Quilter has been doing a Row x Row each year
https://canadianquilter.com/news/row...g-row-4-trees/
more to watch for
https://my.modafabrics.com/inspirati...christmas-2020
blockheads
https://bearcreekquiltingcompany.com...eads-iii-2020/
oh
also
Snowy Days Quilting has been doing QALs
Nothing posted for 2021 yet, but all these are still available to download for free:
https://www.snowydaysquilting.com/quilt-alongs