How does filing the I-526 affect applying for OPT?

It may be fine. An I-526 and nothing more should not give rise to immigrant intent, but you may get some questions about it.

Filing an EB-5 petition on Form I-526 should not impact your Optional Practical Training (OPT) unless you travel abroad. I do not expect your OPT to be denied, but should you travel abroad and need to renew your F-1 student visa or are subject to inspection when you re-enter the United States, the Consular Officer or the CBP Inspector at the airport could question your nonimmigrant intent.

There is no question on the I-765 Form that asks whether you have filed any immigrant petition, such as the I-526.

No, your OPT processing should not be affected by the pending I-526, as long as you have not worked unlawfully or without authorization prior to this point.

While technically the filing of an immigrant visa petition for a permanent green card can impact the processing of benefits such as OPT or temporary student work authorization, in practice we have not seen denials issued on the basis of the filing of an immigrant visa petition alone. Applying for an F-1 OPT visa abroad, should you need to travel, could be more difficult.

EB-5 should affect your OPT. However, with that said, it is best to consult with your investment immigration attorney, as there can be unknown complexity in your personal situation.

It should not, as the EB-5 is for a future application - did you request consular processing or adjustment?