Slow PC upload/download speeds on browser

Hi, for context I'm a cinematographer and a lot of my job involves downloading and uploading files I also play games on the same PC. I mention this because it makes me quite aware of what my average speeds are on the websites and apps I use. that is to say; this is not an issue of what or where I'm trying to upload/download to/from. I don't know my specs off the top of my head but I can get them if needed, I know I've got an Nvidia chip if that matters, and I'm running Windows 11.

Recently (since about a week ago now) my upload and download speed is terrible. For upload, a 10gb file took about 24 hours to upload (MUCH longer than normal) and my download speed floats between 20-150KB/s. I'll tell you what I've tested and solutions I've tried, because the strange part is this:

1) my speeds on all other devices are normal.
2) my speeds on some apps are normal. For example in the steam client & the riot games client, my download speeds were normal. It appears to only be a problem on browsers specifically.
3) both on ethernet, WiFi, and also on a different WiFi connection the issue persisted on browsers alone
4) online in-browser speed tests provide results different to what I actually get (they display 3.5mb/s download and 5.90mb/s upload)
5) file transfers within the PC and between the OC and SSD/HDD are at normal speeds
6) WiFi during live games is fine, but streaming YouTube on my PC browser is slow.
7) some websites load slowly – for example Google docs, gmail – but some don't, for example scouty

I've tried (not necessarily in this order):
1) switching browsers, I've tried several
2) changing between WiFi and ethernet
3) changing WiFi's
4) restarting my router
5) restarting my pc
6) changing ethernet ports on the WiFi box
7) cleaning my pc with dust blower
8) changing DNS to 8.8.8.8 8.8.4.4
9) disabling metered connection
10) scanning my pc for malware
11) disabling vpns and plugins from my browser
12) updating my drivers
13) changing my ethernet controller properties in the control panel from auto negotiation to 100mbps full duplex
14) disabling large send offload ipv4 and ipv6
15) running in CMD center: netsh int in reset
netsh winsock reset
ipconfig / release
ipconfig /renew
ipconfig /flushdns
16) disabling unnecessary startup apps
17) disabling windows update downloads from other PCs in the settings app
18) resetting network in settings app
19) updating windows
20) asking friends (including one who built the pc for me originally)

I have NOT:
1) physically moved my pc prior to initial incident
2) exposed my pc to liquids
3) changed service providers/WiFi plan
4) got VPN/adblockers active
5) taken apart or upgraded the pc since I got it (beyond removing the glass panel for cleaning)
6) reached out to my service provider (solely since it's such a specific issue)
7) taken it to a PC repair shop

Please help. Happy to answer any questions.