As someone who has been alone in some
deeply dark places, I'll share what's worked for me - YMMV.
* You gotta force yourself out. There's no trick, you just gotta fuckin' do it. It's hard. It sucks. You've also gotta do it if only to make sure you're varying your day and creating the opportunity for chance encounters. I spent fifteen months bottled up alone and it was only through the good graces of friends that I didn't...yeah.
* Eat out more, specifically for the human interaction. Find a local restaurant with a good deal on food (like a happy hour), and head there once a week for a meal you didn't make, and to be surrounded by strangers. Even just a "Yes Sir/Ma'am" and similar pleasantries will help, weirdly enough, because it's direct human contact. If there's a trivia night, even better - Buffalo Wild Wings was my brief go-to for that sort of thing.
* You gotta learn to love yourself, somehow. If there's an aspect you don't like, set about fixing it. For me, it was weight and my soft skills, so I worked on both in the time I could with the energy I had. Being alone means if you don't like yourself, you're never going to be in good spirits.
* You're also not really alone, depending on perspective. Setup a bird feeder and just sit and watch it. Talk to the wildlife, silly as that sounds. Your pets help, but they're "at home", while the rest of the world is decidedly not "at home". You gotta get out of the home if you don't want to be alone.
* You mentioned playing games, and I'll add that's actually what kept me sane during those fifteen months of solo unemployment. I joined a multiplayer game server community, worked my way into administration, made friends, ran events. Gaming can be a form of community if it's intentional, i.e. not just joining random lobbies to kill time.
Look, as someone still single at 39 (but blessedly living with my best friends), being alone sucks ass. There's no way around that, even for someone who generally enjoys their solitude. Lacking the warmth and intimacy of another person is debilitating in a way nothing else is, at least to me, but friends do help in their own way. We cook for each other, share our days, treat one another when we're dour, and do what we can to lift others up. So maybe I'm suggesting you reach out to other friends you may have in similar boats, see if they'd like to spend more time together.
Beyond that, some life lessons I've learned since I had more folks come into my life, that I use when I'm feeling alone or lonely again:
* Go to a city at night, downtown ideally. I look around at the empty buildings, the changing lights, the abandoned sidewalks. I remind myself I'm one of eight and a half billion people, on a single planet in a vast galaxy, itself a small part of an immense universe. Weirdly enough, the smallness of being helps me feel less alone, knowing how lucky I am to be amidst all this, right now.
* After the above, I grab a burger and a milkshake, because I deserve it.
* Pop in some earbuds, go outside for a walk, and dance. Fuck the onlookers, just exist for a moment outside your home. Prove to everyone else you're still here.
* VRChat has been damn helpful. Pop on my headset, drop into an avatar that reflects me in the moment, and world hop. Nobody judges what you do in VR, provided you're not breaking instance rules, and there's so many people there to hang out with, all while staying home. It legit got me through COVID.
* Run a game night! Gathering around Jackbox from every corner of the globe for an hour or two of weekly shitposting also got us all through COVID. Just make sure to all be in voice chat or video conferencing to rib one another.
As tired and cliche as this is, the last point I'll say is that this is exactly what the prior phase of your life was: a chapter. Chapters have endings, and this one is no different. Prepare for the long haul, but hopefully you find someone - and something - better, sooner. You're not alone in being alone, but you'll remain alone only as long as you choose to be alone.
Get out there. Force social interactions. Build those muscles.
You got this.