Need help downgrading a router

[Patrick9876]

I currently have an ASUS RT-AX86U (not Pro) running Merlin 3004.388.8_2. I'm completely satisfied with both the hardware and firmware, but both are a bit overkill for my needs. I would like to simplify my setup a bit so my wife has less to deal with when I'm gone, and I think I should address this sooner rather than later. I would like to settle on a WiFi6 router with a reasonably long future and running stock firmware. No Ethernet need for anything beyond 1GB.

However. I'm not gone yet, and I have a few specific needs for the router.

1. It needs an OpenVPN server.
2. It needs to support FreeDNS from Afraid
3. It needs to support CNAME records to its DNS server

I'm not too worried about #1. Many routers include an OpenVPN server.

I don't know about #2. I have no idea what's involved in using a DDNS service not natively supported by a router I assume there's a standard protocol used the routers and DDNS server, and the router just needs URL of the server. Yes? (Of course that doesn't mean there a way to add such URL.)

I don't know about #3, either. I assume (based completely on wishful thinking) that a router natively running OpenWrt or DD-WRT has a way for users to configure its DNS server. Am I dreaming? I asked a similar question some months ago and was told to consider running an external DNS server. I have a couple NAS devices that could support this, but I don't consider that a simplification of my setup. And it didn't answer my question about OpenWrt and DD-WRT.

Should I give up and stick with Merlin?