I wouldn't be waiting for anyone to help me, I would be making arrangements for my teens if they were really struggling, as you have described op.
Book drs app and speak to GP
Book online counselling specialising in teen therapy (do your research)
Organise small outings in the car, moving on to half days out and then full days out
Ask over some friends into the garden for mocktail making or fun activity for an hour, and increase each time.
Speak to family and friends and ask them for support and if possible invitations for dc to spend time with others
Insist on outside exercise once a day
Encourage them to get up earlier, dressed and showered. Its not okay to be holed up in bedrooms all day.
Organise a BBQ and put some music on, bring some fun back into the house. Ask them to contribute to the cooking/menu choices etc
Cooking twice a week for the family
Op get them to reconnect with you, the outside world and keep going. I am worried about my teens. It is not a great time for them at all, but we need to keep going. I don't have the answers op, but can only share with you what we are doing. I am knackered, but I not giving up. Good luck.