The default page does vary somewhat by geography, I think the most recent time I remember discussing the front page with people it was suggested that VPNs probably give it the absolute least to go off of so you'll probably just get the worst stuff with broad appeal.

It does seem like they don't account for IPs of likely VPNs, just for fun I run a few bots which would be using cloud providers' IPs to do stuff like report every video with certain tags for promoting violence, watch only recommendations with <x views from channels with <y subscribers, send a bunch of watch events for specific videos and then do some of that stuff - just seeing if it digs up anything interesting. It used to, but it seems like they've really constrained it lately and now it just falls back to recommending sports & family vloggers. Also it does appear like there's an internal limit on how many channels a user can totally block before it stops respecting those blocks 100% of the time. It probably varies by how many total channels there are that it will recommend.

Clearly what you need to do is run a bot that's constantly doing leftist searches and watching leftist videos on your VPN.