Sorry, that is not going to be possible. You can transfer a host from Win to Win or from Linux to Linux, but not across OSs, because you need the host folders to be on the exact same absolute paths in the new system (https://siawiki.tech/client/transferring_the_client_to_a_different_computer) and the paths in Win and Linux distros are different...

Consider instead a mini-computer, barebone or so, like an Intel NUC (around $150 + whatever you spend in RAM and internal storage). Also if you have a bit more of budget, HP Microservers of 8th generation can be found sometimes on the used market at $300 and they are fantastic hosts in my opinion: ECC RAM, decent CPU, <50W of overall power consume and 4 bays for disks.

Or if you want to use a RPi nevertheless, create a new host on it and retire gently the current one: select "stop accepting contracts" and wait until your current contracts expire (usually 3 months, but you can check the timeline of all of them on https://siastats.info/navigator on the third tab of the search box)