I play the 13x13 a lot on KGS - https://www.gokgs.com/ . Lots of bots there to play with if you feel unskilled to play with a human. With larger boards, the bots seems to be very easy to beat.
I wonder if that gives false confidence, beating the very easy bots.. I get totally crushed by gnugo but I know there are lots of other DDK players I could have a good game with. It'd be neat if go servers (like OGS) had preference flags where you can distinguish between "beginner friendly" and "noob friendly" so that weak and variable 18-23+kyu noob players won't feel like they're wasting the others' time and not feel pressured to resign immediately, or won't feel like they need to treat every non-blitz game seriously with reading and thinking about every move to avoid blunders. When I play in person I have the help of body language and chit-chat to decide whether I should keep on fighting other interesting areas of the board after a blunder or just give up and start another, a lot of people online don't even speak english (or at least very well).