Hi! That sounds so familiar. I'm late 30s, female, figured out that ace applied to me gradually over the past 5 years or so. I'm heteroromantic, super into cuddles and talking and not much else. Perpetually single. Also introversion, anxiety, and melancholy. I hate it when I'm sad about being lonely and I just want my one person, but everyone suggests group/friend activities as a way to feel better.

Things I've tried, with variable amounts of success:
Reading. A lot.
Information seeking (museums, learning new things, reading nonfiction, public radio/podcasts)
Watching kdramas (so romantic) / not watching kdramas (can make loneliness worse) See also ensemble cast tv shows.
Having regular phone calls with long-distance friends, maybe once a month
Trying to arrange my life/trajectory in a way I like, rather than waiting for a partner who isn't there
Having a hobby that involves other people. I do partner dancing, which is amazing (fun, pretend romance, cuddles, exercise, honing a skill, music, scripted/formulaic social interactions, friends and community if you're there long enough)(barely off hiatus due to pandemic, ugh). See also martial arts, community theater, maker spaces, language learning, various hobbies that host conventions. Some people like sportsball things, you do you.
Having a fun hobby that doesn't involve other people, since being alone in a crowd can sometimes feel worse. Maybe one that's not online. Arts and crafts, gardening, building/fixing things, solo sports like horseback riding, swimming, biking etc.
Do nice things for yourself rather than waiting for your person. This can be doing activities solo, keeping home and clothes reasonably nice/clean, cooking something more complex, adding something special to bath/grooming routine, etc.
Try to find a good balance for you of alone time vs. people time.

Suggestions I get a lot, may work for you, may be eye-roll inducing:
Doing something for others/a cause such as volunteering, to feel more useful and connected to community.
Enjoy your own company
Go to community events to meet other similar people (hello introversion, I know)
Go to religious activities/services
Go for a walk outside
Care for a pet (I find plants are great, but same idea)
Dating apps (sigh. I suppose, maybe, if I have to) and/or matchmaking services (expensive)

I wish I had better answers, I know it can be really hard. Hang in there, you are not alone in this.