First it is hard for kids after their freshman year of living off on their own, not being responsible to anyone else. That is an adjustment to go from on your own to being back home. A COVID experience didn't help anyone. You will have to give him leeway in his independence. Once they live back home though they should have some house and family responsibilities. Maybe plan some fun things you know he would normally like to do with family and have some quality time every couple weeks to keep that connect.
You said you are paying his "tuition". Who is paying for his room, board, books, fraternity costs, car and insurance if he has one, cell phone, health insurance, spending money .... If he has a job and he's paying all that, great! If you are still paying all that then you all need to come to an agreement of what you expect from him, life is give and take. And perhaps let him know what you won't be paying for going forward so he can plan .... I know many who make the kids pay for greek life and other clubs because they are not important to getting an education. You sound underappreciated to me, and sounds like you feel that way too. Don't go through the next few years like that.
Also you say he's in his room and with friends .... does he have a summer job? If not I would tell him he needs to go get one asap because this fall he is going to be paying for ..... ex: fraternity, spending money.
My DS decided after year one of concentrated studies that he didn't want to go that route. In essence he would lose the entire year and he was terrified to tell Dad that he was changing directions and pursuing something less lucrative. After year two he hated the small college town atmosphere and wanted to return to big city. Loved his school but found the area was not for him. Again a transfer meant he lost credits. Now he was paying all his own tuition so that wasn't a hurt for us, but he was upset with himself maybe, with the whole process being pushed to commit to the major at 18, for trying to do something Dad would have wanted ... he survived and now has his Masters but there were bumps at times he didn't share with Dad.
Sometimes facing parents with some things whether it is major, grades, social gaffs, something that may have happened at the fraternity ... it is easier to sit alone in a room than feel like you aren't being open. Keep an eye, give him time and if you think something is going on other than growing up pains, perhaps look for a way to open conversation. And hopefully it's just growing pains.