Is bloods clots on lungs and legs related to having subacute lupus?

Autoimmune: Yes lupus even sub acute can cause clotting issues and puts you at a higher risk for blood clots.

It can be: Lupus and other inflammatory diseases lead to hypercoagulability that increases clotting, and certainly can lead to DVT and pe ( clots in the legs, and clots in the lungs).

Possible: Likely circulating anticoagulant - antiphospholipid syndrome.