I've not used it for a few months, but I installed from homebrew as well.

Run `arch` in a terminal. Does it return `arm64`?

Interestingly, I just opened Alacritty on my M1, and it's showing `arm64` now. I know it didn't before. The app has been upgraded because macOS's security tools blocked it when I tried to open it and I had to explicitly allow it.

Maybe it was an issue that they've fixed since I last looked?