I became a single mum when my daughter was 2. I didn't do online dating but went on a few casual dates (an ex-work colleague, and someone from my sports group) when my daughter was 6, then had a FWB for a bit (which was great!), and then had a short lived and intense relationship with someone I'd been friends with for years. I met my lovely partner of 3 years (a single dad) when we became friends at our kids' sports group, when my daughter was 7.
It's quite possible that some men might have put off by me being a solo mum, but the guys that I was interested in weren't.
In your shoes I would probably hold off on dating for a little while, just because relationships can sometimes suck up so much of your emotional energy - I regret my shortlived relationship for this reason.
But I'd recommend doing something 'adult' for yourself once a week or fortnight without your son - eg sports or a dance or art class, or catchup with girlfriends. I have fond memories of browsing bookshops in the evening by myself without buying anything! A FWB can be good if you are sure it will be low drama. It's really important that you have time to do something you enjoy. I know this will be more challenging at the moment with lockdown but there might be online activities you enjoy.
Also, finding other solo mums with kids the same age in your area is really helpful. I made two good solo mum friends through a meetup group when my daughter was very little and they are amazing for doing all the things that I would see two parent families doing together, like weekend outings and holidays. And they are my absolute rocks who I can count on for anything. For me I think that took the pressure off wanting to be in a relationship because I wasn't really missing out on too much.