"No Local Dictionary Available" error from dictionary after upgrading from Sierra to Catalina
I think it's worth trying a reinstallation of Catalina. I've reinstalled macOS countless times to solve odd issues like this and while it may seem extreme, it's quite safe and often the simplest and quickest option.
Make sure the machine is backed up, then restart into the Recovery partition by holding down Cmd-R at startup, then reinstall the OS. It shouldn't take very long and you can set it going overnight or another convenient time.
Your files and settings shouldn't be affected by the reinstallation, but backing up is always sensible in case of (very rare) errors.
If this doesn't work, as a last resort you can try a clean install, and then restore from Time Machine backup, being mindful of @Yoan's warning about mixing Time Machine backups.