You SSH into it. Then do whatever you need to. There's nothing in the UI that can't be done via CLI as far as I know. Some plugins might not be 100% CLI compliant but at least the Base UI (luci) is completely transparent to the CLI via uci.
I haven't done a ton of research in this area, but I'd certainly like to use OpenWRT or OPNSense on my home routers/firewalls.
Side note: I've been trying to figure out a decent way to get rid of Android on my Galaxy S9+, but it appears to be locked.
At the end of the day, I just want to be in control of my bandwidth, my data, and know whats going on. Big companies are making this very complicated with all the tracking.
I recently re-enabled my pi-hole on a virtual machine, and it never ceases to amaze me what is talking to the internet without my permission. After digging into DoH a bit, I'm about to the point where I think I need to put in an outbound proxy, deny all outbound access except via the proxy, and iterate again and again.
I just don't want to have $200 a month in power bills to support my home network to save bandwidth and know what is traversing the net.
That being said there is no hardcore prosumer hardware out there for this purpose. The moment you go beyond home user router hardware like the WRT3200acm you are in either CISCO Buisness stuff or custom server builds. Potentially a Raspberry Pi 4 with a PCIE ethernet card is closest to prosumer hardware out there and there's a lot of hacking involved to get that running to the same degree as a openwrt router
But I doubt most consumers really care. It's complicated.
The R7800 is well supported by OpenWrt, has the hardware features I need, some room to gro, and it's affordable used. I paid about $90 for my first one, and about $70 for my backup unit.
For OpenWrt for smaller purposes, for which an R7800 is both overkill and physically bulky, I understand there are a bunch of near options now. I just keep some old WNDR3700 and WNDR3800 units on hand, which used to be my main routers, and actually still could be. (Sometimes they might be a simple WiFi bridge or print server. Other times, they might be an experimental LAN that needs different properties than I have set up for my main router, and with which I don't want to complicate my main router setup.)
If you don't like the fork, at least with the Turris Omnia it looks like you can put on vanilla OpenWRT [3], but as always check the OpenWRT table of hardware for details before buying.
I think the PSU of the Turris Omnia is rated at 40W max, but I don't know what sort of real-world power draw you'd get with your specific use-case. I guess it depends on whether you use WiFi, the SFP port etc.