it seems 8958 is only for married filing separate couples.
there is IRS PUB 555 which discusses community property reporting
https://www.irs.gov/pub/irs-pdf/p555.pdf
reporting depends on wether you lived apart all year or not
from the pub
Spouses living apart all year.
If you are married at any time during the calendar year, special rules apply for reporting certain community income. You must meet all the following conditions for these special rules to apply.
1. You and your spouse lived apart all year.
2. You and your spouse didn't file a joint return for a tax
year beginning or ending in the calendar year.
3. You and/or your spouse had earned income for the
calendar year that is community income.
4. You and your spouse haven't transferred, directly or
indirectly, any of the earned income in condition (3)
above between yourselves before the end of the year.
Don't take into account transfers satisfying child support obligations or transfers of very small amounts or
value.
If all these conditions are met, you and your spouse must
report your community income as discussed next.
generally, the one that earned the income reports it - wages, business income, separate property income, social security benefits and certain other categories
Other income. Treat all other community income, such as dividends, interest, rents, royalties, or gains, as
provided under your state's community property law.
if not apart all year
Other separated spouses. If you and your spouse are
separated but don't meet the four conditions discussed
earlier under Spouses living apart all year, you must treat
your income according to the laws of your state. In some
states, income earned after separation but before a decree of divorce continues to be community income. In
other states, it is separate income.
the IRS does not have a form for your situation.
