MyRocks collation support assumes the collation has PAD attribute (except for BINARY/VARBINARY). It was actually quite difficult to achieve this.
Then, MariaDB got some collations that have NOPAD attribute. MyRocks code needs to be adjusted to handle that.
Probably the easiest first step is to just disallow indexed NOPAD columns for MyRocks tables.
Then, the second step would be to actually enable support for them