I have two 401k's. I maxed 401k #1, and put nothing in 401k #2. If I receive a 1099R code 8 (overcontribution) with a $15k disbursement from 401k #1, can I put it in #2?

No, you can only contribute to the annual limit ($20,500 for 2022 and $22,500 for 2023). If you withdrew only the excess plus earnings then you reached already the maximum contribution limit.

The $15k returned was due to discrimination testing, not because I contributed more than $20500. If you subtract the $15k returned to me, then I only contributed $5,500 to my 401k in 2022.

Please, be aware that the deadline to contribute to the 401(k) for 2022 was December 31, 2022. 

Yes, as long as you didn't contribute more than $20,500 total for both the 401(k) you are fine.