Currently, Geyser support is very limited: Bedrock players can't see any textures. It might be possible to add full (or just more) support. This documentation might help: https://github.com/GeyserCustomModelData/HowTo
If not, their Discord server might provide some help.

Whole currently, Geyser is working towards adding Bedrock custom model data (and have reached some success) they have still not added support for blocks.

Interesting... if this issue would be solved entirely on the Geyser side, I might not even need to do anything myself (or at least do less work).

Here is how.

1. Download and install this version of geyser on your server (https://ci.opencollab.dev/job/GeyserMC/job/Geyser/job/feature%252Fextensions/)
2. Get a direct download link for your java resource pack
3. Go to this converter, and open an issue to convert your pack (https://github.com/Kas-tle/java2bedrock.sh/actions)
4. Once your pack is converted, go to the action run, and get your pack
5. From the .zip archive take the geyser_resources.mcpack and the custom_mappings.json
6. Put the .mcpack in the packs folder and the .json I the custom mappings folder
7. Let bedrock players join and download your pack

Note: If something is wrong with the bedrock pack, check the action run log to see what went wrong.

To see the status of the project and upcoming updates, check here (GeyserMC/Geyser#210). If you want to see an example of a converted pack, check here (https://www.dropbox.com/s/0n0o0ax110382qj/Archive.zip?dl=1).

KCI 13 will have reasonable Geyser support, but it won't be complete because that's very hard/impossible.