A note on the Fanless devices in an enclosed space: this isn't really a problem in most cases, even in a small closet (non-walk-in) they will do just fine. A 7th or 8th gen i5 (Qotom in this case) at medium load on a 1Gbps WAN-LAN type of configuration with no active airflow runs at about 30°C here. Because the chips used are low-power and/or mobile variants, they are designed to run fine even when hot (think: 100°C!).
If you can get a Topton, go for it, Qotom would be a good choice if you don't need 2.5GbE yet, and most other brands generally derive from those (or are just white label variants of the same thing).
On the other hand, you can run an mATX device with large fans at a slow speed just fine. Even with no case fans and just a PSU and something like a Cooler Master tower cooler (very cheap yet very performant) with a relatively large fan you can get a pretty quiet setup. That said, if you want to prevent the accumulation of even more stuff, you can also make the choice to only buy new stuff if something else goes out the door.
If you can get a Topton, go for it, Qotom would be a good choice if you don't need 2.5GbE yet, and most other brands generally derive from those (or are just white label variants of the same thing).
On the other hand, you can run an mATX device with large fans at a slow speed just fine. Even with no case fans and just a PSU and something like a Cooler Master tower cooler (very cheap yet very performant) with a relatively large fan you can get a pretty quiet setup. That said, if you want to prevent the accumulation of even more stuff, you can also make the choice to only buy new stuff if something else goes out the door.