Personal Thin Client

Mods: Apologies if the post is not relevant in this sub. If so, please redirect me and I'll move it to the appropriate sub.

I have a Mac mini for Mac OS, Lenovo Thinkstation for Windows 10 and a VM on a Synology Diskstation running Linux. Is there a personal solution (like the VMware Horizon Client) that I can use on one laptop and access all three systems? I am aware that using a MacBook, I can access the mini (Screen sharing), RDP app for Windows and (maybe) free VNC and OpenVPN for the linux VM on the NAS (haven't tried it yet but should be possible).

My concern is the cost. Getting a MacBook Pro just to be a thin client would be pretty expensive. Are there any open-source solutions that I can install on a cheap/used 17 laptop to make this possible?

Thanks.