The official Geyser versions only support 1.20.80 - 1.21.2. Any other builds that appear to support more versions are likely using custom builds.
The reason we're not supporting more versions are relatively simple:
- Bedrock auto-updates, so few people are using older versions (and, downgrading isnt easily possible on most platforms)
- Versions before 1.20.80 do not have all of the new 1.21 features, such as items/blocks
- With the removal of older versions, we were able to remove a few ugly workarounds that are no longer necessary, cleaning up the codebase.