It’s been an underdeveloped topic for some time. espeak-ng is available on most distros and has some integrations available that somewhat tie it into the desktop. There are more modern solutions that sound way better. For example Coqui’s xtts2, maybe Piper which is part of Home Assistand nowadays. If your language is English, you got quite some more solutions available to choose from. But it’s a mixed bag if they sound nice, are easy to install (that also depends on which Linux distro you use and if it’s available as a package) and if they tie into the rest of the system. I’m not an expert on this, but I’d also like to have TTS and STT available on my Linux desktop witout putting to much effort into it.