The partnership owns a home?   Or the partners use their own homes?

They use their own home.

So 8829 doesn't actually need filed but just use it to calculate deduction?

Correct, it is only used as a worksheet.  Actually, you don't even need to use Form 8829, you can use the worksheet in Publication 587.
https://www.irs.gov/pub/irs-pdf/p587.pdf#page=20

I had my first one of these that went with Sch E this year, I used a dummy Sch C to compute the 8829, printed it (got rid of the Sch C/8829) and then just entered the amount on the Sch E.

Good idea.

Thank you. This information is very helpful.