The beat must march on, as evidenced by the fact that the Sound! Euphonium anime adaptation is continuing in various forms. The latest to be detailed is the previously announced OVA, which is officially set to premiere in Japan in summer 2023. That puts it nicely ahead of the 2024 plans for the third season, and you can see a teaser trailer and visual for the OVA below.
The first two seasons of Sound! Euphonium are currently available to stream on Crunchyroll, which describes the series like so:
Spring in the first year of high school. Kumiko, a member of the brass band in junior high school, visits the high school brass band club with classmates Hazuki and Sapphire. There, she comes across Reina, her former classmate from junior high. Hazuki and Sapphire decide to join the club, but Kumiko can’t make up her mind. She recollects her experience with Reina at a competition in junior high school.
Source: Official Twitter