there are distros that run on debian sid, if you prefer debian as a distro, but want a more up to date experience.
im running pika os, because it offers up to date gaming tweaks, but doesnt force you to update as often. keep in mind: that os is not something i would recommend for a environment where stability is the goal, because there are only a few maintainers. its just an example of debian sid!
i bought a asrock n100 board and put 2 additional nics on it. then i configured ipfire with the red, green and orange mode. (red = wan, green = lan and orange = dmz) that way i can self host a vps inside the dmz and run the lan network without a vlan. i dont know if thats the best way to do it, but there are so much new things to learn i still dont know anything about and want to keep it as simple as possible.
you could start with a simple thin client with multiple nic‘s and get a similar price then my n100 with 4gb ram but i wanted the ability to swap some parts if needed and thin clients are rather limited in that aspect. edit: also i needed a nic with poe for my wan and thats hard to find in a regular thin client. i didnt search that hard though.
im in the same boat as you. tried opnsense for a week, but the webui is really not that friendly for a total beginner like me. im running ipfire right now, which offers less options but thats a + while im still learning the basics.
boxes is great, if you just want to try a distro and are already on linux.