You dont necessarily need FttH to get faster than gigabit speeds.
There are cable modems with ethernet ports that put out 2.5Gbps on a standard ethernet cable and you can buy a 2.5GBaseT SFP adapter which works fine on the Turris Omnia. See my post here: FS 2.5GBase-T SFP not working with Turris Omnia - #7 by tac2
I use Comcast which gives me 1.2Gbps over standard coax cable and my cable modem has a 2.5Gbps WAN port which is connected to my Omnia’s SFP port using CAT6 cable.
The SFP port does support direct fiber if you can get it from your cable company though (though I dont know which adapters are supported by the Omnia, see the wiki Supported SFP modules [Turris wiki] )