Just beware last I checked they're not very active compared to the reddit. Getting into a lot of trackers on open signups tends to rely on someone posting about it within hours of it happening. Unfortunately less people use lemmy so they're less likely to post about it here, it's not like they have some person in all the trackers who keeps an eye out, it's entirely up to someone noticing and making a post. Some may open for only 24 hours (hawke tends to I think).

So regardless of where you see something open, if you have a place you want, I recommend signing up immediately within minutes rather than waiting even an hour as you never know how long it's been open before it was posted about or how soon it will close. Just make sure you read the rules and any newsposts for new users within the first 24 hours if you can as some places may require activity in the first 24-48 hours for new accounts.