ah youre so welcome kitty.. theres many different ways to find a beta, but all of those kind of involve being active in the community.. if you have a twitter account thats linked to your ao3 account and have posted some fics out there, youll have a few followers already, and its always worth it to do a quick post and just ask if anyone has the time to beta for you.. or you go find minsung ao3 writers discords and they might have a channel to ask for betas. Or if you join events such as slickfest or minsung ficathon you can sign up to get a beta assigned to you!
its always worth to ask, and my only advice is to try your best not to overthink it... you can be scared of rejection but it hasnt killed you yet so even if it hurts its still worth to ask until someone answers..... but. my prefered way of getting betas is to make writer friends! thats also scary oviously bc anything social is scary but if you can manage to build a fun online friendship with other minsungers, theyre very eager to give you their attention and support you in your fics ! And ALSO be the person tht approaches people for betaing too, if you see anyone ask.! even if you think youre not "good" at it, most people really just need someone to look at their fic and tell them "yes this makes sense. also theres typos in these places" and also give them praise too.. and you can do that!! and you might get closer to these people and they might be people you can approach for betaing your stuff too...
its just a kind of natural progress of being involved in the community. yk . and it might take some time to get betas if you dont have a lot of eyes on you but its not like you need one to write fics. so just like. keep writing and posting to your hearts content and ocassionally ask for betas and i bet someone will bite eventually...
anyway... i hope this helps you.. good luck kitty..