FairPhone 4 not only promises 5 years of android software updates but also has 5 years of warranty, There are more reasons to trust their words than any of the other phone manufacturers.
• They are not profit focused but rather towards sustainability, They have been delivering their promises consistently for 8 years and so it's not an idealistic vaporware.
• They produce the most repairable smartphone using components sourced from conflict free areas. Parts for repair are available directly on their site, Parts for FairPhone 1 are still available.
• Their factory workers get living wage bonus, Of course do not employ child labor while preaching humanity.
• They have first class support for alternate operating systems i.e. We are the owners of what we buy; So support from alternate OS like Linux, Sailfish or even android ROMs like LineageOS could exceed even the official 5 years support.
FairPhone4 hardware is competent enough for average daily use, Only drawback I see is that the phone is available only in Europe. Then again Google Pixel phones have been notorious for being available in only couple of countries.