AWeber supports DMARC compliance via SPF and DKIM authentication.
Contact AWeber support for DKIM configuration. For more information visit: https://help.aweber.com/hc/en-us/articles/360023682313-How-do-I-set-up-DKIM-and-SPF-records-for-my-domain-
There is evidence that traffic for your domain from AWeber can authenticate SPF properly. However please read: https://help.aweber.com/hc/en-us/articles/4410070518427-Do-I-need-to-update-my-domain-s-SPF-record-The-answer-is-No- If you wish to pursue authenticated SPF from AWeber, you will need to work with their support. Until/unless you do this, you should not have an SPF record entry for this traffic.