Surprisingly, Umami has been handling our traffic volume without breaking a sweat on much smaller instances. I suspect PostgreSQL's superior handling of concurrent writes plays a big role here compared to MySQL/MariaDB. Except for the team/user management, everything feels much nicer on Umami.
Shameless plug: As part of the migration, I also took the opportunity to learn some Rust by writing a small utility that uses the Umami API to generate daily/weekly analytics reports and sends them via email[1]. Pretty happy with how it turned out, though I'm still learning Rust so any feedback or suggestions for improvement are welcome!