Connected to Wi-Fi but no symbol- Safari works, but apps aren't? (Very weird issue, please help!)

Hi all,

Using an iPhone 8 Plus, updated to iOS 14.4 (latest update as of this issue).

tl;dr: Settings says I'm connected to wifi but my 4G symbol doesn't change to the Wi-Fi symbol.

I can search pages in Safari and they DO load (with my cellular data turned off) but any other apps using internet don't work. This happened overnight (so not after any updates of anything) and is the same at home and work, so I'm sure it's my phone and not my router/modem.

This morning I woke up (last night everything was working fine) and tried to watch a YouTube video- the page loaded, and the ads and suggested videos below all loaded their thumbnails, but the video itself stayed on the spinning loading wheel.

I noticed my 4G symbol was up, but Settings says I'm connected to the Wi-Fi. Safari pages do load, even with cellular data turned off, but I tried a speedtest and got 0.00 in the download part and it just didn't progress from there, so.. zilch. Very weird.

I tried Airplane mode on/off, Forget This Network (at both home and work) and Reset Network Settings. Each time my phone says it reconnects to my Wifi network (a tick next to the name and everything), but only once did the 4G symbol flicker to the Wifi symbol for a second. Other than that, no change. I'll do a DFU reset tonight and try resetting from my latest iCloud backup, but any specific help would be greatly appreciated.

If it matters, I got my screen and battery replaced about a week ago, but everything's been fine since then.