I will admit that I haven't read the full thread. I'm sure there are lots of useful suggestions, as well as some less useful ones. May I add my tuppence worth?
You have no hobbies? Well, find some. At a very low point in my life, I got myself a basic selection of acrylics and a couple of canvasses. Totally life-changing! Creativity I didn't know I had started pouring out. Via YouTube I found online friends with similar interests.
Years earlier, similar experience with music. More recently, cat rescue and fostering. The point is to engage with things that mean something to you. Friendships will follow. You are not the only Eleanor Rigsby! There are people out there wanting to connect, but they won't come floating into your life unless you reach out.
In the meantime, plan your days. Exercise (YouTube has some excellent workouts), shopping, a nice walk, watching some of the excellent events being streamed online (National Theatre, Wigmore Hall, Met Opera, ROH, ENO - there is so much!! Every major European orchestra, opera, theatre company etc are streaming 😎).........
And perhaps reach out to people? You are not the only one who finds lockdown difficult. Some of my closest friendships are the result of my 'reaching out'. Be courageous! The worst that can happen is a non-response.
NB: The Six Pillars of Self-Esteem by Nathaniel Barden is a good read.