Surely AWS is the worst choice for this given that bandwidth is the main resource that VPNs consume, and AWS bandwidth is ludicrously expensive. For the €5/month that Mullvad charges for unlimited bandwidth you can only get about 60GB of EC2 egress even in the cheaper regions.

If you're in Europe, just take a scaleway stardust for €4/month with unlimited traffic :)

AWS Lightsail is made for that. VPS with 2TB of bandwidth for $5/month.

According to vantage comparator, t4g.nano (the cheapest) is $3.50 monthly, but you (probably) need to factor in public IPv4, which is $3.60 if I calculate correctly, unless you do funny hacks with port forwarding via SSM. But this is irrelevant when you factor in data transfer.