The Playable RealTracks should be working on Drums but they haven't got them enabled yet as they maybe creating some more kits for the PG Sforzando library.
If you load Sforzando into a Utility track and choose a PG Drum Kit,
you can then select Piano Roll, select a Utility track, drag n drop a midi drum solo into it setting the bars in to position the midi.
Go into the Audio Edit for the RealDrum track and mute those bars that have midi using the Volume Automation.
Adjust the volume of the midi drums to match the RealDrums.

Videos: BB22-Drum-Solo.mp4
BB22-Drum-Solo2.mp4

MidiSolo to try DrumSolo.mid
You can use DRUMSOLJ.STY and Force Midi Drums as Jim suggested, you can generate up a midi drum solo track in another instance of Biab, play through to find the riffs or rolls you like then just highlight those bars on the Chord Sheet, now drag the Drum track at the top of BB to the MID Drop, when green drag and drop into the other instance of Biab choose the track and position.
You can import any section from any midi file drums you may have.
Also in the Midi Import dialog select Merge so it won't erase any other solos you dropped in before.

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