In general I dislike fixed adapters like that as they put unnecessary strain on the host USB port. Even a small tethered cable is better IMO.

TP-Link has a USB-C version of its UE300 USB-A to GbE adapter, and the USB-C one is currently on sale for the same price as the fixed adapter you linked in the selftext.

So sorry to hear this! It's such a frustrating issue. For setting up an ethernet, you'll need to find wherever the ethernet port is in the wall of your house/room. I'm not sure if all houses have them, but this is what my wall port looks like: https://www.lowes.com/pd/RCA-RCA-CAT5e-6-Network-Wall-Plate/5001717657?cm_mmc=shp-_-c-_-prd-_-elc-_-ggl-_-LIA_ELC_204_Surge-Safety-Multimedia-_-5001717657-_-local-_-0-_-0&ds_rl=1286981&gclid=CjwKCAiA3L6PBhBvEiwAINlJ9Np_NLTq1BFUQBHPnFgBFbS1JT5-tfTj6YSs_CUxjOPhbnOUDmjmiBoCVJcQAvD_BwE&gclsrc=aw.ds

Once you've located your ethernet port, you're going to need to plug in the ethernet cable into it. Here's one option if you need an ethernet cable: https://www.amazon.com/Cat6-100ft-Ethernet-Network-Internet/dp/B07D7RVL65

As for adapter, if you have a MacBook, you can either buy apple's version or amazon. Both probably work pretty well:

Apple: https://www.apple.com/shop/product/HJKF2ZM/A/belkin-usb-c-to-gigabit-ethernet-adapter

amazon: https://www.amazon.com/TP-Link-Ethernet-UE300C-Compatible-2017-2020/dp/B08HQBC678

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As for Firefox vs Chrome, I don't know if one is better than the other. I was using Chrome, and never tried Firefox since I don't have it downloaded. Definitely might be worth trying out.

Let me know if you have any other questions! Best of luck with everything.