I'm currently on this path, happy to share what I've learned so far. Hit me up on DM (wait, does Lemmy have DMs??), to connect and talk shop on Discord.

Develop a prototype. I like to do this digitally (tabletop simulator, tabletopia, screentop.gg). I made a YouTube video on how to make cards, there's plenty of tutorials on making a digital prototype for the platforms I listed (here's a video tutorial for screentop that a friend made). For physical prototypes, Adam in Wales covers the basics.

Playtest. You'll need to playtest, a lot. Like way more than you think. Friends and family don't count, they're obligated to be nice and supportive. Bring your game to your local boardgame store and cajole and/or bribe people to play. As the other comment suggests, best results will come from saying you're testing someone else's game. Anonymous feedback forms can work well too. Be gracious about receiving feedback, these folks are helping you make your game better. Don't argue even if you disagree, accept it all and thank everyone for their time.

Join a game design / playtesting community. Lots of these for digital playtesting on Discord (protospiel, break my game, virtual playtesting, remote playtesting, indie game lab, etc). If you're in or near a metropolitan area there's a good chance of a local game designers meetup. Boardgame conventions usually have an Unpub room where you can book a table and folks will stop by and play. Playtesting with game designers is the best way to get really insightful feedback into your game.

Once you've done all that and still have a game you'll have to decide whether to pitch to publishers or self-publish. There's pros and cons to both sides so do your research here. Lots of content out there on this, Stonemaier Games blog is a good starting point.