Changing DNS does not "take effect"

Question

I've been trying to troubleshoot this for the past 2 days, I've tried so many things and I'm just tired and need help now.

First, a short description of my whole network:
I get service from 2 different ISPs.

1. ADSL on a TP-Link router (I connect to this via wifi)
2. Mikrotik SXT 5HnD (Wireless P2P AP) to a D-Link router via ethernet and that's connected to my PC via an ethernet cable

I have access to both TP-Link and D-Link routers, but not the Mikrotik AP.
PC is running Windows 10, latest update. (I do not believe this is an OS issue, as the problem persists on Linux, will explain more later.)

I've been trying to change my DNS to a new one that's closer to me. But no matter where I set the DNS, whether it's in Windows or my router, my ISP seems to just ignore them and uses something else.
This has led me to believe that even my previous 8.8.8.8 and 1.1.1.1 DNS settings were not really used either. (Not sure) I have set the new DNS in both my router settings and in my Network Connection adapters, both on wifi and ethernet (IPv4 properties)
I've tried the ipconfig commands in between the changes, such as "release, renew and flushdns".

The DNS I'm trying to use has a website that tells you whether or not you have set the right DNS and it is working. I know that feature works for a fact, since I made a 3G hotspot with my phone and I set the DNS on Windows and It worked. However it's not ideal since I need my main internet connections to use this DNS, not my 3G hotspot.

Last night I setup a Raspberry pi with DNSMasq as a DNS cache and I assigned the new DNS as the only server in dnsmasq configuration file. Then I assigned my Raspberry pi's IP as my DNS on my PC and in my routers.
This did not work either. I thought maybe using a dnsmasq would force the DNS, but nope.

I've tried booting into Ubuntu with a USB drive and doing the same things in there, and it still does not use the new DNS. This is what has led me to believe it not an OS issue.

I'm at a loss since I've been unable to find a common ground between these 2 routers and completely separate ISPs to see what could possibly be causing this issue.
I know people who are using the same new DNS and they have no issues.

I've done a lot of troubleshooting in the past 2 days, so there's probably a few things I've forgotten to mention here. Any help would be really appreciated.
Thank you