

What is typically done, e.g. buying a PinePhone with PostMarketOS or refurbished setup deGoogled Murena phone, is having a default user with a well known password, e.g. 123456. AFAIR when you setup Rasbian you do have an interface to have a default user with a password.
I personally made an ISO of a configured distribution, see https://fabien.benetou.fr/Cookbook/Electronics#SocialWebXRRPi0 and that worked quite well for my use case.
I bet you can find stuff on AliExpress for a lot less but then you have to insure support is descent.