As it is common for mods to take time to update, it often leads to modded servers having to stay on older versions, such as mine. Geyser-Standalone and Geyser-Proxy solutions (e.g. Geyser-Velocity, Geyser-ViaProxy) was the solution for running GeyserMC on servers running older versions. But a problem arises as Hydraulic, targeted at modded servers requires to be installed on the backend server with Geyser on the _latest release_, and as of making, Geyser does not multiple versions at the same time, with the only solutions to get Geyser on older versions being the ones aforementioned. Which don't involve Geyser being installed on the backend server.
The following is all a suggestion on how it could be possible to resolve the issue:
You could take the same approach as with how Floodgate supports Geyser-Standalone and proxies. Where you have Floodgate installed on the backend server (which can be an older version compatible with the server) and you would need to import your key.pem file into the proxy/Geyser-Standalone for verification. While also having to set auth-type to Floodgate in the config for Geyser-Standalone. Except with Hydraulic, you would put a version of it that supports the server version on the backend, put a similar alternative to the key.pem file that would go on the proxy/Geyser-Standalone and have a setting in Geyser-Standalone's config for Hydraulic. However, Geyser-Standalone would also have to support Hydraulic like Floodgate, and there would need to be a proxy version of Hydraulic.
The issue is getting the Geyser API for Hydraulic. Without MORE internal changes to Hydraulic, maybe a special version of Geyser with just the parts of the API needed for Hydraulic would be installed on the backend server, serving as a possible solution.
As it is common for mods to take time to update, it often leads to modded servers having to stay on older versions, such as mine. Geyser-Standalone and Geyser-Proxy solutions (e.g. Geyser-Velocity, Geyser-ViaProxy) was the solution for running GeyserMC on servers running older versions. But a problem arises as Hydraulic, targeted at modded servers requires to be installed on the backend server with Geyser on the _latest release_, and as of making, Geyser does not multiple versions at the same time, with the only solutions to get Geyser on older versions being the ones aforementioned. Which don't involve Geyser being installed on the backend server.
The following is all a suggestion on how it could be possible to resolve the issue: You could take the same approach as with how Floodgate supports Geyser-Standalone and proxies. Where you have Floodgate installed on the backend server (which can be an older version compatible with the server) and you would need to import your key.pem file into the proxy/Geyser-Standalone for verification. While also having to set auth-type to Floodgate in the config for Geyser-Standalone. Except with Hydraulic, you would put a version of it that supports the server version on the backend, put a similar alternative to the key.pem file that would go on the proxy/Geyser-Standalone and have a setting in Geyser-Standalone's config for Hydraulic. However, Geyser-Standalone would also have to support Hydraulic like Floodgate, and there would need to be a proxy version of Hydraulic. The issue is getting the Geyser API for Hydraulic. Without MORE internal changes to Hydraulic, maybe a special version of Geyser with just the parts of the API needed for Hydraulic would be installed on the backend server, serving as a possible solution.