What's the least painful PM setup for a small startup?

We're a small team and don't really need a giant project-management setup.

Most of our work already happens in Slack. The problem is keeping track of all the "can you handle this?" and "I'll take care of that" moments without creating another admin job.

I'm looking for something that can organize tasks from Slack, follow up when something is sitting there, and ideally do a bit more than just send reminders.

Pondros came up while I was researching Slack-native options, but I'm curious what other startup teams use.

What's your setup?