Who has personal experience with it in terms of support, how often and for how long are updates available?
I currently have Huawei P30L and Nokia 5. Before that, Samsung wasn't that happy.
I want to spend max 400 euro can also be refurbish / used.
Google is the best manufacturer for early Android updates. They also develop Android.
Updates are guaranteed for 3 years on Google smartphones. I think there are security updates every month punctually on the first day or shortly thereafter. New Android versions are also available on the first day or shortly thereafter.
https://support.google.com/...7705?hl=de
I would recommend the Pixel 4a for around 340 euro (new).