I know a person I helped to do just that!
You want your contacts in .vcf format. Look on that weird Apple store, I found an app, it had ads but it was able to export the contacts.
You can use Localsend to transfer all your stuff, or pay the Syncthing for IOS App which probably works better. IOS has some arbitrarily low limit on shared pictures.
No idea about calendar but you may want .ics or something else.
In general, Apple stuff is not well transferrable and that is their fault. Welcome to the bright side!
The hardest change will be passwords. Password managers on Android suck, but Bitwarden or KeepassDX are FOSS so you have that.