I had same issue, my wife too. I was so frustrated I decided to start reading and watching everything I could on WiFi issues on iPhone, not just 2020 SE. I eventually came across a video that made me look for something and I just changed a setting that, after 20 mins, auto connects to my home WiFi like my iPhone 7 and iPad does. Hope it continues to work, if you’ve been having the same problem with WiFi not connecting and/or dropping connection on your iPhone SE 2020, try this..
>Settings
>Privacy
>Location Services
.......scroll to bottom of menu
>System Services
.......Networking & Wireless was turned off, try turning it on and then cycle power to you phone
.......You may need to connect to your WiFi manually for the first time, but after that mine functions just like my trusty old iPhone7
Worked for me 😀
BTW, while you are in this menu, checkout what else is turned off, many things for me, I turned a few of them on while I was there, like Cell Network Search, HomeKit, and Motion Calibration and Distance. Not sure how so many services got turned off, I’ll play with them to see what affect they have on my apps.
Let me know if this works for you, cheers.