All ISP provided
router ONU combo units are useless as routers.
Likely Downsides (depends on what you get):
- Everything will be locked down; you will likely not even be able to change DNS server in DHCP settings. This is a huge privacy issue.
- Buggy firmware leading to random issues and poor reliability as ISPs are cutting corners
- Lack of DFS channel support, resulting in poor performance in congested apartments.
- Only 2x2 MIMO, resulting in poor performance when using multiple devices.
- Only Wi-Fi 4 in 2.4GHz band, so poor performance if you stray too far from your router.
- Lack of WPA3, as it is optional for Wi-Fi 6. Neighbour kid with an ESP8266 can enjoy your connection for free.
- Poor gaming performance due to bufferbloat and cheap hardware.
- Higher idle power consumption due to cheap hardware combined with the beefier specs required for Wi-Fi 6.
- All LAN ports will still be 1GbE
IIRC, you only pay for the number of days you use a plan, which means you can bait them into installing a Wi-Fi 6 router by paying just a few hundred extra instead of 3K more for a month. I'm not sure if this works before the first bill, if it doesn't, you'll be left paying ₹100-₹120/day or ₹3000-₹3500 extra for an entire month over the much more reasonable plans. That money could go into buying a decent router.
Personally, point 1 alone strikes out any ISP provided equipment as router for me. My use cases (gaming, wireless VR, file transfer, etc.) also strike out cheaper WiFi 6 routers, ISP provided or not.
I thought about doing this too, but as of now I am using a
Mercusys MR90X, which I got for a pretty good price of 9K last year, it has none of the downsides I mentioned and has a pretty decent Filogic 830 chip which supports OpenWRT. I use it only for Wi-Fi 6 devices while the rest of devices go on an older AP. It is running in bridge mode with the Airtel provided crap ONU.
If I feel like cleaning up my setup or adding battery backup, I will buy my own ONU with SN cloning but from what I read, it can be a hit or miss depending on what OLT is being used and I don't notice any major issues with the provided ONU router combo acting as a dumb media converter.