COVID has caused most everyone to experience more isolation, but this can be particularly difficult for those of us with mental illness. The isolation can cause us to lose more connection to reality and to think darker thoughts.
There are some good mental health forums at Reddit where people are supportive of one another. They are divided by illness (e.g., bipolar forum, psychosis forum, etc.). You can also contact your local NAMI (National Alliance on Mental Illness) and find out if they are hosting groups, lectures, etc. There are 600 NAMI locations in the U.S. and I've had some very positive experiences with mine.
If possible, have someone (neighbor, friend, etc.) check up on you regularly, just to call or drop in and spend time interacting. It really helps. And of course see a mental health professional on a regular basis so you can share your concerns and receive professional support. Though COVID has limited some opportunities, there are still volunteer programs running that you may be interested in joining, too.
Lastly, if you are over 50, you may also want to consider joining AARP's Friendly Voice Program. I've been in it for nearly two years and can't recommend it enough. Once a week, a different volunteer calls you and chats for about 20 minutes or so. They keep notes about your interests, life situation, health, etc. so will tailor the calls just for you.
The volunteers come from all walks of life, are knowledgeable, friendly, and encouraging. When a bond forms -- some volunteers find that you and they share common interests and enjoy each other's company -- those volunteers will make an effort to call you every so often so that you have an ongoing relationship with a familiar person.
To enroll, just call 888-281-0145 and give your name, phone number, and dates/times when you are available to chat.
But in sum, don't give in to the isolation/depression cycle. It's brutal. When we're depressed, we tend to isolate. And the isolation causes us to get even more depressed. Reach out for healthy interaction (which is what you've done through your post) and you'll get the help you need. Don't give up.