The builder_v21 image has now been updated to include both player version 2.01 and version v3alpha11 software. By default, v2.01 is installed, but one can switch versions at any time by connecting over serial and issuing either of these commands: switch_to_v3alpha11 or switch_to_v2.01

There are default empty databases installed by the builder for both versions, but after switching from one version to another you'll likely want to rebuild the database if you have any tracks/playlists installed. Do so thusly:

rw
player ## Wait for player to rebuild databases and start up, then..
## Hit control^C to interrupt the player
ro
exit


Done.