It depends on what you want to do. Those devices with a DSL modem that is supported by OpenWrt are simply quite old and not very powerful. They might work okay as bridged modem only, but do not have enough CPU cycles to do much more. Personally I got a cheap BT HomeHub5a with the intention to make it my all-in-one dsl-router, but got disillusioned pretty quickly (it now serves as bridged modem, still running OpenWrt and feeds a slightly more powerful OpenWrt WiFi router). I can sympathize with the charm of an all-in-one solution, but for DSL that simply is not a realistic option, but see below.
There are dsl-modems in SFP form factor that can be used in OpenWrt routers with an SFP-"cage", but make sure to research compatibility between router and SFP-module before purchase ;). AFAICT, getting line statistics from such a SFP-dsl-modem seems hard to impossible.
Now depending on the router, it might also be compatible to SFP-modules for the different FTTH-options.
But realistically, I would try to solve the current challenge with current devices and tackle the FTTH challenge once it actually materializes at your home, no?
P.S.: One of the options of a OpenWrt based router with an SFP cage would be the turris omnia, but if you start searching the Forum you will see that it has at least as many disappointed users as happy ones.
Disclaimer, I am happy with my omnia, but I do not do anything demanding/bleeding edge on it, nor do I use the SFP cage.