While there are a ton of standup tools out there, I'm of the mindset that you should only jump first to tools if you're looking to make something that is already working more efficient. In your case, standups aren't working, so we need to target the approach.
Daily standups tend not to work for remote teams because they are attempting to do too much. You're trying to fit status updates, blocker resolution, team alignment, and socialization into one 15-minute meeting. Check this out if you're interested in a detailed explanation of why this just doesn't work.
So what's the alternative? Unfortunately, there's no one-size-fits-all solution, so it depends on the team. To start, ask your team what they like and dislike about your current standups. The best people to tell you how to fix it are the ones dealing with it.
When I'm brought in as a Fractional COO for a new remote team, I often find that transitioning to a 'my-week' channel is a flexible and effective solution. At the beginning of the week, team members add their bulleted list of what was accomplished last week and what they plan on doing this week. Here's what that looks like: