This may all be repetitive too since we don't know just what you have and haven't tried already.
-- Try repositioning and re-configuring your router so it's able to emit a stronger WiFi signal with longer coverage range. There's apparently an issue where the cellular signal from the closest cell tower/access point is stronger than the WiFi signal from your home router. Below is a link to a handy guide on setting up a home router with optimal performance:
https://arstechnica.com/gadgets/202...ntific-guide-to-wi-fi-access-point-placement/
Install this 'WiFi Analyzer (open-source)' app on your phone to help set up your router. Don't just make assumptions and guesses that you're getting good WiFi coverage, take steps to get actual data to confirm there is adequate WiFi signal strength wherever you need it. Use the utility to make up a rough heat map of coverage so you know weak and strong points, and be sure to test both 2.4GHz and 5GHz band networks.
-- Just assuming you've already done this but just in case delete and re-enter the WiFi network entry in your phone to see if that makes any difference. Also, is your Poco phone having similar problems with other WiFi networks or just one in particular? (the former might indicate a networking issue with your phone, the latter to be with just that local network).
-- You might want to enable the 'Aggressive Wi-Fi to Cellular handover' option in your Poco phone. It's an option buried in the Developer options menu you need to enable first to access it:
https://android.stackexchange.com/q...-cellular-handover-option-in-developer-settin
This option is intended to make the automatic changeover from a weak Wi-Fi signal to a cellular signal less likely to occur. If you find it to be too 'aggressive' just disable it.
-- On the router, set up a temporary guest network using just the basic default settings. Then see if your Poco phone has any connectivity issues with that temp WiFi network. If it's still a problem, than there is some issue between your phone and that router, if not than that indicates there's some quirky configuration setting with that particular WiFi network. You might think that simply because other devices are not having the similar issues that it has to be a problem only with your phone, but keep in mind basic networking is much more complex than that. You might want find it less of a hassle to narrow down the exact setting problem and just set up a new, clean WiFi network, and then just reconnect all your devices to that new network instead. In that case , it's a good time to lock down your router to further protect your local network from nasty crap that's now pervasive in the open Internet:
https://routersecurity.org/index.php
