This is straightforward with browser addons like uBlock Origin where you can add and choose blocklists, but I did searches for doing so system wide and using a VPN but didn’t find clear answers. I could use a DNS service that provides blocklists but isn’t it best practice to leave DNS to the VPN provider? I looked up blocklists and VPNs but didn’t find relevant results.
On Android, I didn’t find any apps that let you filter blocklists and using your own VPN other than Rethink, but the blocklists feature requires using Rethink’s DNS.
So what’s the best way to filter ads and trackers on both 3rd party apps and on OS’s like Android (specific Samsung phones) while still using a VPN?
Essentially, you outsource the blocking to your VPN server in that scenario. You can have a blocklist of advertisers, trackers, or bad-behaviour like SSH/HTTPS scans, etc. You would generally download a list of misbehaving netblocks and block them on your firewall, then download a list of known-bad domain names, and block them from being resolved by DNS (i.e. just return 127.0.0.1, which is your local device, which always fails)