EDIT: So because of my $0 budget and the fact that my uptime is around 50% (PC, no additional servers) I ended up using NextDNS. For the time being it works (according to dnsleaktest), an added benefit was improved ad-blocking (100% in this tool). I now have plans for a proper router in the future with a Pi-hole. Thanks so much for all the info & suggestions, definitely learnt a lot.
So it turns out I got myself into an ISP that was shittier than expected (I already knew it was kinda shitty), they DNS hijack for whatever reason and I can’t manually set my own DNS on my router or even my devices.
Cyber security has never been my forte but I’m always trying to keep learning as I go. I’ve read that common solutions involve using a different port (54) or getting a different modem/router or just adding a router.
Are they all true? Whats the cheapest, easiest way of dealing with all of this?
Adguard home is a better choice as it supports DoT and DoH, which OP will need to use to be able to bypass their ISPs DNS hijacking.
Pihole only supports unencrypted DNS on port 53 which is what the ISP is targeting.