I've been trying tmux and followed a video that showcases and offers a prebuilt config for styling and plugins. Something happended (guess I did something wrong?) the styling broke and I decided I'll go bare bones and customize to my needs when needed instead of using preconfigured stuff. I deleted all configs and caches I could find with fzf and even reinstalled tmux, but still some broken styling is present and makes it unpleasent to work with. Some of my configs seem to be present even after uninstall, as the prefix is still C-Space instead of the default. There are some oh-my-zsh subfolders that contain tmux. I don't know if those have been there before and I also don't know, if I can delete them without breaking the next thing.
I'm on a MacBook and installed tmux via brew.
Feels like a font issue. Do you have e.g. nerdfont installed and in use in your terminal? You could check the config for plugins that makes that style, and check which fonts are in use. Could also be powerline fonts that are needed: https://github.com/powerline/fonts
I got the JetBrainsMonon Nerdfont. It was annorphan process of tmux still running after all configs and tmux itself was uninstalled.