UnRaid may be exactly what you are looking for. It's similar to proxmox, but UnRaid has a plugin called "Community Applications" where people make pre-configured Docker containers that most of the time only need the user to define a path for saving files (though some do need more configuration).
UnRaid boots from a USB to RAM. So it's hard to get lighter weight than that! You don't even "install" it, per se. You can pop it into a computer with an already installed OS, boot via USB, and then can boot the native OS as a VM in UnRaid, if you want. Then shut down, remove the USB, and reboot to the original OS as if UnRaid never existed. Now there's caveats and pitfalls if you are not careful. Don't go formatting drives if you do it that way or making major changes as it could affect the native OS install if you're not careful. Im just letting you know it's possible.
Using the built-in Docker in UnRaid, those services get dynamic access to the computer's resources and have minimal overhead when idle. VMs, I believe, have more overhead. So this may allow you even more capability on an old laptop.
I've never used Docker before, but I now run Home Assistant, Plex, Immich photo backup, minecraft server, Trilium Notes, Blender, Cura Slicer, and a couple others all as Docker containers. All I did was click install, add path to folders, and then they were up and running!
One of my favorite things about how UnRaid works with Docker is that all your Docker containers are set up to be accessible on your network, by default, and can be viewed on any web browser with access to your network. When I want to show off a little, I pull up things like Blender on my smart tv. It's a terrible user experience trying to use a remote as a mouse, but I'm able to "use" Blender on my TV it I so feel!
But mainly, I like to sit outside on nice days and have access to my computer from any device on my network. I'm working on making things accessible over vpn for me and a few services by reverse proxy for friends. But I'm still learning.
Search UnRaid's Community Applications page for services you run and see how many are already available. https://unraid.net/community/apps
There's also youtube videos on making your own programs available in UnRaid. You can also add personal Docker containers through Docker Compose.
Plus, UnRaid makes settings up VMs very easy. So, if you just want to have a program in a VM for ease of use, you can do that too!
I have only ever used UnRaid, so I can't speak to the differences between server options. But I love UnRaid!
I am not very experienced in using text-based command terminals, so having a GUI is very helpful for me. In the past, I've tried to really understand the Linux terminal, making reference sheets for all the commands and writing down file paths, but in the end, I just spend way too much time trying to remember/ figure out how to do something that would only take clicking an icon. (I'm not here to argue the merits of terminal vs GUI. I understand the power of the terminal and still occasionally use it when necessary).
I originally started using UnRaid because of the Linus Tech Tips video, where they made 2 gaming PCs in one computer. I really wanted to do that too for my partner and I to game together. I mainly wanted to do that for the cool factor, but ultimately, it was cheaper to buy all the parts for one PC and just get a second GPU and an UnRaid license than it was to buy everything for 2 PCs.
UnRaid's built-in Docker and VM support is amazing! The Community Applications plugin has also made Docker Containers a breeze! People make pre-configured apps that only take minimal setup on my side to get running (mostly setting the file path for save folders). I've never made much luck with Docker itself on other OSs, but now I run Plex, Home Assistant, Blender, Cura Slicer, photo backup, minecraft server, etc. All only took a few clicks and setting file paths, and then they are up and running!
The ability to quickly spin up VMs in UnRaid and choose how many resources you want to give it (CPU cores, RAM, passing through USB or any PCIe device) has been amazing! It is really making it easier for me to learn Linux since I can easily access Windows or Linux as VMs and easily give GPU access to either if I need to. I guess it's like having all the benefits of bare metal installs and VMs.
UnRaid also has a terminal for more advanced users. Really, it seems anything is possible with some of the stuff I've read about people doing. And I never imagined I could build two gaming PCs into one!