I always ride solo - 7,000+ miles last year, indoor and out.
I will just echo what others have said.
Use some of your time for training be it speed, endurance, breathing, pedalling technique, even fuelling.
Plan rides and explore, I use Strava’s route planner, but also export to OSMand app on my phone. I can then use overlays to map out shops, cafés etc. But I still carry too much!
3-4 times a year I will have a solo overnight stay with my bike and camping gear. Total relaxation!
What I love about riding solo is that everything is your decision. Sometimes that can be negative and you can talk yourself out of riding.
So set yourself weekly and monthly challenges, another nice Strava feature, it really motivates if the boredom does set in.