There are more. MNet has already been mentioned. Then there is iomad https://www.iomad.org/ and also https://docs.moodle.org/en/LTI_and_Moodle. But your previous comment "We need to have to [two?] separated Moodle instances, which are not on the same servers anyways" tends to eliminate them.
Oh yes, we are looking for a technical solution to a problem caused by a non-technical decision.