I think the right decision would be letting Rasmus Hojlund go and meet his master at Bayern Leverkusen since ETH is also considering coming for him, Napoli is also interested.
Serie A will be the best option for him, moving to the league he was once comfortable at before his move to Man United and at Napoli he has a better chance of medal and improvement under the management of Antonio Conte than under his former coach at United who signed him but couldn't bring the best out of his signing. While Bundesliga is not really tasking in compare to the EPL moving back to Serie A is better for him.
Returning to Erik Ten Hag fold isn't the right choice for Hojlund. I mean at the very least, he should be able to work under a different coach. Conte has a unique way of making useless players useful. For example McTominay who was considered a bad player by Ten Hag has become a driving force at Napoli. If Hojlund wants to improve his skills, Napoli is the most logical choice.