Nie, nie ma żadnych. Zacytuję też stronę, która weryfikuje niektóre wątki z serialu:

Theres no evidence that Aethelred was a cruel husband to Aethelflaed

The thing to mention here is that Aethelred and Aethelflaed seem to have cooperated, they seem to have had a joint position and thats probably because in order for Aethelred to have some sort of quasi-royal authority in Mercia, hed have to emphasise Aethelflaed, his legitimate wife with royal blood, in his position there.

link: https://www.denofgeek.com/tv/the-last-kingdom-how-historically-accurate-is-the-n etflix-drama/

Co do jego charakteru, jest wzmianka z biografa króla Alfreda, niejakiego Assera, że Aethelred odznaczał się "tyrańskim zachowaniem" wobec walijskich państewek.